Our Collective Tensions: Paradox Research Community’s Response to COVID-19

In this commentary on three articles from dozens of paradox theory scholars on paradox approaches to examining the COVID-19 pandemic and how the COVID-19 pandemic informs paradox theory, the authors involved in coordinating the collection of three papers discuss the process of bringing together scholars from around the world to discuss the pandemic. Four other preeminent paradox theorists offer additional commentaries on the papers in this Collection.

The History Boys: Critical reflections on our contributions to Management Learning and their ongoing implications

In this reflective essay, written for the 50th anniversary of Management Learning, we look at the history of the journal from a unique vantage point, our interconnected, academic lived experience of publishing in the journal. Our aim is to undertake an historical review of our publications in Management Learning in order to identify the key themes of our work, to make connections with broader academic and social events of the time and to assert the continuing relevance of these themes for future scholarship. We review 27 papers that we have published in Management Learning since Volume 1 (1971) and identify four main themes from our papers. These are set in the context of the development of critical management education. We highlight the broader dimensions to our themes and suggest two areas with implications for future scholarship in Management Learning. In our conclusion, we use our findings and reflections to identify what we have learned about management learning, as well as making a call for action in relation to what we are labelling historical reflexivity.

Reflections on the Role of Bemusement in Institutional Disruption

In this essay, I reflect on the disruptive potential of bemusement. When people are bemused, we feel confused or bewildered. We can also feel wry pleasure, especially if we are bemused by something perplexing, that confounds expectations or norms. I explore how the affective tensions of bemusement can unsettle persons’ emotional investment in institutional order. I argue that disruption arises from surfacing the absurdities that are part of what is accepted as normal, and I illustrate this with a discussion of the “Dismaland Bemusement Park.” I assert the importance of confounding stability, order, and rationality by recognizing the parallel existence of confusion, absurdity, and illogics. Practical access to these parallel dynamics arises from the art of cultural subversion. Such an art both politicizes and gives pleasure to those involved in disruption and it embraces the ensuing confusion as a critique—as a potentially insightful twist on institutional order.

Putting the contradictions back into leadership development

Purpose

The purpose of this paper is to outline an alternative view of leadership development that acknowledges the likelihood of unintended and contradictory outcomes in leadership work. Helping leaders to engage with contradictions is as important as developing their positive capabilities. A focus on the contradictions of leadership can help to address the emotional and political limitations that development programmes unwittingly impose on learning.

Design/methodology/approach

The paper discusses how leadership development currently falls short in helping people to lead in complex organizational environments. This argument is illustrated by examples taken from MBA teaching programme in a School of Management together with an analysis of contradictions in the National Health Service Healthcare Leadership Model. The final section gives four examples of how to put the contradictions back into leadership development.

Findings

The paper does not seek to present empirical findings. The illustrations support an argument for changes in practice. Examples are provided of a different approach to leadership development.

Originality/value

The paper critiques approaches to leadership development on the grounds of its relentless positivity regarding leadership behaviour and that focusses primarily on the development of individuals. Attention is called to the contradictions inherent in leadership work which extend to the leadership development process itself. Once acknowledged, these contradictions offer important leadership learning opportunities for both individuals and organizations.

The learning organization as paradox

Purpose

This paper aims to describe and discuss the idea of the learning organisation as a paradox and to explore the implications of this idea for improving the longevity and influence of the learning organisation concept.

Design/methodology/approach

The paper presents qualitative data drawn from MBA students’ involvement in learning about leadership. Participants’ written reflections on the “Temporary Learning Organisation (TLO) Exercise” are used to illustrate paradoxical tensions emerging from their attempts to lead the emergence of a learning organisation.

Findings

Three inter-connected paradoxical tensions are identified: inhibited freedom, detached engagement and ambivalent enthusiasm. These can help to explain how processes and practices that encourage learning in organisations are inseparable from those that undermine the effort to learn.

Originality/value

The paper presents a novel way of looking at the debate between the learning organisation as a positive ideal, and the learning organisation as negative ideology. A paradox viewpoint is focused on sustaining tensions because they generate possibilities. There is much to be learned from the interplay between the desire to create ongoing learning opportunities and conscious and unconscious efforts to avoid and undermine them.

Finding critical action learning through paradox: The role of action learning in the suppression and stimulation of critical reflection

In this article, we highlight paradoxical tensions generated by in-company action learning. We consider the implications of these tensions for critical action learning, which has critical reflection as a core element of its theory and practice. Using paradox theory as a lens, we analyze data from two in-company action learning programs and build a model relating to critical action learning that has four interlinked features. The model can help evaluate in-company action learning with a view to identifying emotional and political dynamics that are open (or closed) to critical reflection. Such identification assists in making judgements about the appropriateness of critical action learning within a specific organizational context. Our broader contribution is to frame action learning and critical action learning not only as separate approaches but also as potentially interlinked stages in an ongoing process of individual and organizational learning.

Organizing Reflection

The aim of this article is to consider what is involved in the practice of reflection for organizational learning and change. My emphasis is on reflection as an organizing process rather than on the individual, `reflective practitioner'. I describe a way of `organizing reflection' that can create and sustain opportunities for organizational learning. After a brief explanation of the company involved and the action research, I explore some of the literature on reflection. I continue by describing four reflective practices. These are: peer consultancy groups, role analysis and role analysis groups, communities of practice, and group relations conferences. I explain and explore each of these and define their impact at different levels of organizing. Collectively, these four reflective practices constitute an approach to reflection that represents one way of organizing for learning and change.

The Impact of Caution and Blame on Organizational Learning

The aim of this article is to examine the relationship between emotion, learning and organizing. In particular, this involves developing an understanding of how emotional and political aspects of organizing can shed light on the tensions between individual and organizational learning. The research highlights organizational dynamics created through repeated patterns of caution and blame within a public sector organization. The study shows how these dynamics inhibited processes of reflection and communication within the organization, undermining the implementation and further development of strategies explicitly designed for organizational learning. The article explores the politics that arise from attempts to organize learning, as well as how organizational politics are created from and reinforced by emotions expressed both individually and collectively. The final section covers discussions on the contribution of this study to organizational learning, the implications of the study for organizations, and issues for further research.

Emphasizing Learning in Management Research

This paper explores what may be distinctive about management research undertaken from a perspective on management learning. There are some general principles that influence research in this field and the author sets these in relation to key issues that seem to have a particular influence on the learning process. The objective is to present a framework of questions which might particularly represent aspects of research within management learning, and the general phrase used to depict this framework is the notion of 'research as learning'. Such an approach is interested in the integration of specific dynamics that are part of the processes of both research and learning. The paper describes how these dynamics can be utilized in the process of management research, placing specific emphasis on what learning means within, and how it affects the practice of, research in management learning.

The Upside of the Downside

In this paper we suggest that it is important in management education to work with the defensive dynamics in learning groups. Through a consideration of the dynamics within complex systems, we argue that the ways in which these defensive dynamics are worked with may determine the levels of learning attained. This work requires a recognition that defensive dynamics within groups can limit learning, an awareness of the nature of such dynamics, and skill in adopting appropriate strategies in relation to them. Both staff and learners can contribute to this work.

Paradox, Defense and Attachment: Accessing and Working with Emotions and Relations Underlying Organizational Change

Our intention in this article is to add to the different ways of looking at and working with change in organizations. We suggest a set of working propositions that move away from problem-solving or planning-based approaches to change, towards a method which focuses primarily on organizational members' emotions and relations, and on forces of uncertainty and defensiveness. We attempt both to highlight the dynamic nature of change, and to point towards some key issues, often avoided, for engaging with aspects of change. We then describe a participative research process we have employed to access and act on organizational members' emotional responses to change. In this instance, drawings were used with managers in six public service organizations as the catalyst to enable managers to bring out often paradoxical emotions, and to work with these as part of the process of the management of change. While our research is set in the context of enormous changes in U.K. public services, we feel that our methodology is applicable to any organizational setting which is characterized by uncertainty and defensiveness.

Learning about Management: An Analytic Large Group in a Management Development Programme

The author describes the use of a Group-analytic approach within a local government management development programme, in particular during the `large-group' sessions. Large-group sessions seem particularly effective in demonstrating the extent to which a manager is both committed to and able to understand and work with change.

Violent Innocence: A Contradiction at the Heart of Leadership

The aim of this article is to inform a shift from the idea that we need to have “better leaders” towards a better appreciation of emotions and power relations that make leadership possible and impossible in practice. The article makes two inter-connected contributions to knowledge. First, “violent innocence” is introduced as a construct that is helpful in understanding inter-personal and organizational processes of projection and denial connected to leadership. Second, the construct is used to comprehend a “structure of innocence” in organizations arising from symbolic violence and connected to destructive relations of power that are accepted as normal. Three illustrations of violent innocence are discussed and linked with contradictions that are integral to leadership in practice. These contradictions emerge from particular dynamics: that leadership is often undertaken in a hostile environment covered up with positivity; that it is informed by strategies that create relations of dependence and domination; that it is inseparable from the exercise and experience of power; and that it is bound up with projective dynamics that connect the “unwanted self” of the leader with systemic processes of destruction. The article concludes with a discussion of the productive consequences of integrating the “dark side” into our understanding of leadership practice.

The effects of low and high glycemic index 24-h recovery diets on cycling time trial performance

AIM

The present study investigated the effects of high and low glycemic index (GI) 24 h recovery meals on the physiological responses and subsequent athletic performance, following a glycogen depleting protocol.

METHODS

Ten well trained cyclists (age, 33.6±7.4y, height, 175.3±7.6 cm, weight 74.5±8.2 kg, and VO(2max), 60.5±6.0 ml∙kg(-1)∙min(-1)) participated in two trials in a randomized cross- over design. On day 1, subjects performed a glycogen depleting protocol after which they then consumed either high or low GI recovery diets over the next 24 h, which provided 8 g.kgBW(-1) of carbohydrate. On day 2, the subjects returned to the laboratory, 2- 3 h postprandial, to perform a 40 km time trial (TT) on the Velotron cyclePro© ergometer.

RESULTS

No difference was observed in TT performance times between the high GI (93. 5±9.29 min) trial and the low GI (90.7±11.1 min) trial (t=1.1; P=0.35). Additionally, no differences in carbohydrate (F=1.1, P=0.37) fat (F=1.1, P=0.40) oxidation or blood glucose concentration (F=0.9, P=0.5) was observed.

DISCUSSION

The results of the present study suggest that the ingestion of a high GI carbohydrate 24 h recovery diet following glycogen depleting exercise, has no greater effect on endurance performance than consuming a low GI carbohydrate 24 h recovery diet. It may be concluded from these results that, provided enough carbohydrate is consumed during a 24 h recovery period, there is no difference in subsequent endurance performance.

The spatial psychodynamics of management learning

This article addresses the question: how can we help managers to understand the emotional and political dynamics that surround and permeate their managerial roles? A conceptual framework is presented that is based on the integration of literature on space with literature that has taken a psychodynamic approach to management learning. The term spatial psychodynamics describes the way in which juxtapositions of material, relative and relational space in the management classroom can reveal dynamics that help managers to perceive the emotions and politics that are part of their roles. Three characteristics of spatial psychodynamics are presented: unconscious dynamics and the interpretation of learning space, the political effects of fantasy in learning space, and how juxtapositions of space create distinctiveness of place. An example is discussed in order to illustrate how this concept can improve our ability to engage with emotional and political dynamics in the management classroom.

Ultrasound enhanced detection of individual meningococcal serogroups by latex immunoassay

AIMS

To examine A, C, Y, and W135 Neisseria meningitidis serogroup characterisation by ultrasonic standing wave enhanced latex agglutination tests (USELATs) of clinical samples. In addition, to determine USELAT enhancement of detection sensitivity for the individual antigens compared with conventional card latex agglutination tests (LATs).

METHODS

Wellcogen (Abbott Murex), Slidex meningite kit 5 (bioMerieux), and Pastorex (Sanofi) kits and beads coated in house with antibodies to Y and to W135 alone were tested. Positive control antigens consisted of A and C polysaccharide preparations and the Pastorex Y/W135 kit sample. The limiting concentrations of antigen detection were determined by USELAT and by LAT. Thirty five clinical samples (plasma), previously characterised by the polymerase chain reaction (PCR) and culture, were tested by USELAT and, when sample volume allowed, by LAT.

RESULTS

USELAT enhancement of control antigen detection ranged from 16 to 128 fold for the different latex systems. Enhancements for the different control antigens were comparable between kits. USELAT tests of clinical (A/C/Y/W135) samples (n = 15) with the Wellcogen (A/C/Y/W135) and Slidex meningite (A/C/Y/W135) kits showed comparable specificities. A set (n = 22) of Y and W135 samples gave 18, 19, and 17 positive results for Wellcogen (A/C/Y/W135), Pastorex (A/C/Y/W135), and in house beads (Y/W135), respectively. Positive USELAT PCR and culture results were concordant. A typical sensitivity for the commercial kits was 80% (Wellcogen).

CONCLUSIONS

USELAT identified serogroups for 80% of samples, whereas LATs identified only 40%. The USELAT detection of the A, C, Y, and W135 antigen serogroups showed comparable enhancement for the kits tested. The commercial availability of latex beads coated with antibody to the Y and W135 serogroups would expedite their identification.

Metabolism of O6-propyl and N6-propyl-carbovir in CEM cells

The metabolism of O6-propyl-carbovir and N6-propyl-carbovir, two selective inhibitors of HIV replication, has been evaluated in CEM cells. Both compounds were phosphorylated in intact cells to carbovir-5'-triphosphate. The metabolism of these two agents was inhibited by deoxycoformycin and mycophenolic acid, but not erythro-9-(2-hydroxy-3-nonyl)adenine. No evidence of the 5'-triphosphate of either compound was detected in CEM cells.

Substrate specificity of human glycinamide ribonucleotide transformylase

The nucleotide substrate specificity of human glycinamide ribonucleotide transformylase, a chemotherapeutic target, has been examined. The enzyme accepts the sarcosyl analog of glycinamide ribonucleotide, carbocyclic glycinamide ribonucleotide, and two phosphonate derivatives of carbocyclic glycinamide ribonucleotide with V/K values, relative to that obtained for beta-glycinamide ribonucleotide, of 1, 27, 1.4, and 2.9%, respectively. Several other analogs of carbocyclic glycinamide ribonucleotide, namely a truncated phosphonate and 2',3'-dideoxy- and 2',3'-dideoxy-2',3'-didehydro-carbocyclic glycinamide ribonucleotide, were inhibitors of the enzyme, competitive against glycinamide ribonucleotide, with Ki values approximately 100 times higher than the Km for -glycinamide ribonucleotide. Although the results of the present study parallel those obtained previously with the avian enzyme (V. D. Antle, D. Liu, B. R. McKellar, C. A. Caperelli, M. Hua, and R. Vince (1996) J. Biol. Chem. 271, 6045-6049), quantitative differences between the two enzyme species have been uncovered.

Synthesis and activity of gamma-(L-gamma-azaglutamyl)-S-(p-bromobenzyl)-L-cysteinylglycine: a metabolically stable inhibitor of glyoxalase I

The inhibition of glyoxalase I enzyme to increase cellular levels of methylglyoxal has been developed as a rationale for the production of anticancer agents. Synthesis of a peptidomimetic analog of the previously prepared potent glyoxalase inhibitor, S-(p-bromobenzyl)glutathione (PBBG), was accomplished by inserting a urea linkage, NH-CO-NH, to replace the gamma-glutamyl peptide bond. Thus, the target compound, gamma-(L-gamma-azaglutamyl)-S-(p-bromobenzyl)-L-cysteinylglycine 6, was a potent inhibitor of glyoxalase I with almost no loss of activity when compared to PBBG. However, unlike PBBG, 6 was completely resistant to enzymatic degradation by kidney homogenate or by purified gamma-glutamyltranspeptidase enzyme.

A highly efficient synthesis of cyclaradine and its behaviour towards adenosine deaminase

(+)-, (-)-, and (+/-)-Cyclaradines were efficiently synthesized from 2-aza-bicyclo[2.2.1]hept-5-en-3-one (ABH). (+)- and (+/-)-Cyclaradines were deaminated by adenosine deaminase whereas (-)-cyclaradine was not hydrolyzed under the same conditions.

Deamination of cyclaradine by adenosine deaminase under high pressure

The deamination of cyclaradine corresponding to a carbocyclic analogue of ara-A having anti-HSV activity by adenosine deaminase was examined under various pressure. The deamination of (+)- and (+/-)-cyclaradine was remarkably facilitated by high pressure, and the rate was increased with increasing of pressure. However, (-)-cyclaradine was not deaminated even under high pressure.

Lack of mitochondrial toxicity in CEM cells treated with carbovir

Carbovir (CBV) is a guanine nucleoside analog with potent in vitro anti-HIV activity. A prodrug of CBV is currently being evaluated in clinical trials as a potential agent for the treatment of AIDS. The ability of CBV to inhibit mitochondrial DNA synthesis in intact CEM cells was evaluated in the present study, because most of the currently available anti-HIV nucleoside analogs have significant toxicities that result from their inhibition of mitochondrial DNA synthesis. No delayed cytotoxicity was observed in CEM cells treated with 50 microM CBV for 4 weeks. In addition, CBV at concentrations as high as 1 mM did not cause a decline in mitochondrial DNA levels and only minimally increased the concentration of lactic acid in the medium. In contrast to these results with CBV, treatment of CEM cells with 0.5 microM 2',3'-dideoxycytidine resulted in delayed cytotoxicity, a decrease in mitochondrial DNA content and increases in lactic acid levels in the medium. These results indicated that treatment of CEM cells with CBV did not result in the inhibition of mitochondrial DNA synthesis and suggested that treatment of AIDS patients with CBV, or a prodrug of CBV, would not result in some of the toxicities seen with the other anti-HIV nucleoside analogs.

Substrate specificity of glycinamide ribonucleotide synthetase from chicken liver

Several analogs of glycinamide ribonucleotide and phosphoribosylamine have been prepared and evaluated as substrates for glycinamide ribonucleotide synthetase purified from chicken liver. Glycinamide ribonucleotide analogs include side chain modifications wherein the glycine side chain (R = CH2NH2) has been replaced by R = CH2NHCH3 and R = CH2CH2NH2, ribose ring replacement by chiral cyclopentane and cyclopentene derivatives, and phosphate replacement by phosphonates. All of these, with the exception of the O-phosphonate, served as substrates for the reverse enzymatic reaction, with Vmax values comparable to that obtained with glycinamide ribonucleotide, although the Km values ranged from 21 to 118 times the Km for glycinamide ribonucleotide. Analogs of phosphoribosylamine examined as substrates for the forward reaction consist of chiral derivatives of cyclopentane and cyclopentene and a chiral carbocyclic phosphonate. These also served as substrates, with Km values ranging from 5 to 23 times the Km for phosphoribosylamine and with diminished Vmax values. These studies have begun to define the structural features of the nucleotide substrate necessary to support enzymatic activity. Sarcosine (N-methylglycine) and beta-alanine were also accepted as substrates, albeit with reduced affinity compared with glycine.

Substrate specificity of glycinamide ribonucleotide transformylase from chicken liver

Several glycinamide ribonucleotide analogs have been prepared and evaluated as substrates and/or inhibitors of glycinamide ribonucleotide transformylase from chicken liver. The side chain modified analogs, in which the glycine side chain, R = CH2NH2, has been replaced by R = CH2NHCH3 and R = CH2CH2NH2, are substrates, with V/K (relative intensity) of 2.4% and 16.3%, respectively. Several carbocyclic analogs of glycinamide ribonucleotide, including the phosphonate derivative of carbocyclic glycinamide ribonucleotide, did not serve as substrates, but were inhibitors of the enzyme, competitive against glycinamide ribonucleotide, with Ki values ranging from 7.4 to 23.6 times the Km for glycinamide ribonucleotide. However, the O-phosphonate analog of carbocyclic glycinamide ribonucleotide did support enzymatic activity, with V/K (relative intensity) of 0.8%. In addition, glycinamide ribonucleoside was neither a substrate for, nor an inhibitor of, glycinamide ribonucleotide transformylase. Furthermore, alpha-glycinamide ribonucleotide had no effect on enzyme activity. These studies have begun to define the structural features of the nucleotide substrate required to support enzymatic activity.

Comparative brain exposure to (-)-carbovir after (-)-carbovir or (-)-6-aminocarbovir intravenous infusion in rats

PURPOSE

Evaluate the ability of (-)-6-aminocarbovir ((-)-6AC) to improve the CNS exposure to (-)-carbovir ((-)-CBV).

METHODS

Activation of (-)-6AC in vitro was assessed by incubations of rat brain tissue homogenates. The in vivo brain exposure to (-)-CBV was then examined in rats after iv infusions of either (-)-CBV (n = 4) or (-)-6AC (n = 5). The drugs were infused to steady-state via the jugular vein. At the end of the infusion, a bolus of [3H]inulin was injected via the femoral vein in order to obtain an estimate of the brain vascular space.

RESULTS

(-)-6AC was converted to (-)-CBV by incubations of rat brain tissue homogenates. After iv infusion of (-)-CBV, the brain/blood concentration ratio of (-)-CBV was 0.032 +/- 0.009. The brain/blood concentration ratio of (-)-CBV after iv infusion of (-)-6AC was 0.080 +/- 0.020.

CONCLUSIONS

(-)-6AC improved the brain delivery of (-)-CBV, although the absolute exposure of the brain tissue to (-)-CBV was still quite low.

Metabolism of carbovir, a potent inhibitor of human immunodeficiency virus type 1, and its effects on cellular metabolism

Carbovir (CBV) [the (--)-enantiomer of the carbocyclic analog of 2',3'-dideoxy-2',3'-didehydroguanosine] is a potent inhibitor of human immunodeficiency virus type 1 (HIV) replication in vitro. We have characterized the metabolism of CBV and its effect on cellular metabolism in an effort to better understand its mechanism of action. CBV was primarily metabolized to the 5'-triphosphate of CBV (CBV-TP) to concentrations sufficient to inhibit HIV reverse transcriptase. Infection of CEM cells with HIV did not affect the metabolism of CBV. In CEM cells, there was no evidence of the degradation of CBV by purine nucleoside phosphorylase. The half-life of CBV-TP in CEM cells was 2.5 h, similar to that of the 5'-triphosphate of zidovudine (AZT). However, unlike the levels of the 5'-triphosphate of AZT, CBV-TP levels declined without evidence of a plateau. CBV did not affect the metabolism of AZT, and AZT did not affect the metabolism of CBV. A small amount of CBV was incorporated into DNA in intact CEM cells, and this incorporation was increased by incubation with mycophenolic acid, an inhibitor of IMP dehydrogenase. CBV specifically inhibited the incorporation of nucleic acid precursors into DNA but had no effect on the incorporation of radiolabeled precursors into RNA or protein. CBV did not decrease the level of TTP, dGTP, dCTP, or dATP. These results suggested that the cytotoxicity of CBV was due to the inhibition of DNA synthesis. Further studies are necessary to identify the target(s) responsible for growth inhibition.

Synthesis and biological evaluation of 5'-sulfamoylated purinyl carbocyclic nucleosides

The first series of 5'-sulfamoylated carbocyclic purinyl nucleosides was synthesized and tested for antitumor and antibacterial activities. The target compounds were formed by reacting the 2',3'-acetonide-protected carbocyclic nucleosides with sulfamoyl chloride, followed by deprotection. The agents were tested for cytotoxic activity against P388 mouse leukemia cells. Two compounds, 5'-sulfamoyl carbocyclic adenosine (2) and 5-sulfamoyl-8-aza carbocyclic adenosine (6) exhibited IC50 values as low as 62 and 15 nM, respectively. These analogs inhibited protein biosynthesis and slowed down DNA and RNA biosyntheses in the P388 cells. None of the target molecules were as potent against Escherichia coli as they were against the tumor cells. Also, in cell-free systems, agents 2 and 6 were more effective inhibitors of protein synthesis in rabbit reticulocyte lysate than in E. coli. These new carbocyclic derivatives appear to be somewhat selective for eukaryotic over prokaryotic cells in affecting translation.

Pharmacokinetic evaluation of (-)-6-aminocarbovir as a prodrug for (-)-carbovir in rats

The recently synthesized carbocyclic 2',3'-didehydro-2',3'-dideoxy-6-deoxy-6-amino-guanosine [(-)6AC] was evaluated as a prodrug for carbovir, carbocyclic 2',3'-didehydro-2',3'-dideoxyguanosine [(-)CBV] in seven male Sprague-Dawley rats. A randomized three-way cross-over design was used. Rats were assigned to receive the following treatments: a 20 mg/kg (-)6AC infusion, 40 mg/kg (-)6AC orally, and a 20 mg/kg (-)CBV infusion. Blood samples were collected over 480 min, and urine was collected for up to 48 hr. A 2- to 3-day washout period was observed between treatments. Following i.v. infusion, (-)6AC concentrations in the blood declined rapidly in a monoexponential pattern with an elimination half-life of 11.3 +/- 3.3 min (mean +/- SD, n = 7). The time-averaged total body clearance was 115.7 +/- 32.6 ml/min/kg. The fraction of the dose excreted unchanged in urine was 0.28 +/- 0.06. The fraction of the (-)6AC dose metabolized to (-)CBV was 0.48 +/- 0.14. Following oral administration of (-)6AC, the bioavailability of (-)CBV was 46.2 +/- 9.9% (n = 6) in comparison with the bioavailability of approximately 20% previously obtained after an oral dose of (-)CBV. The Cmax of (-)CBV after a 40 mg/kg oral dose of (-)6AC was 1.65 +/- 0.7 micrograms/ml as compared with the previously reported Cmax of 1.00 microgram/ml obtained after a 60 mg/kg oral dose of (-)CBV. (-)6AC has considerable potential for the improvement of the extent of absorption of (-)CBV from oral dosing.

Synthesis and biological evaluation of 4-purinylpyrrolidine nucleosides

The synthesis of several novel carbocyclic purine nucleosides that incorporate a nitrogen in place of carbon 3 of the cyclopentyl moiety are described. These analogues are all derived from the key stereochemically defined intermediate N-(tert-butoxycarbonyl)-O-[(4-methoxyphenyl)diphenylmethyl]-trans- 4- hydroxy-D-prolinol (19), which was accessible in 61.1% overall yield for a five-step sequence starting from cis-4-hydroxy-D-proline. The heterocyclic bases, 6-chloropurine and 2-amino-6-chloropurine, are efficiently introduced onto the pyrrolidine ring via a Mitsunobu-type coupling procedure with triphenylphosphine and diethyl azodicarboxylate. Standard transformations and removal of protecting groups gave the cis-adenine (26), hypoxanthine (27), 2,6-diaminopurine (28), and guanine (29) D-prolinol derivatives. In addition, a related sequence from trans-4-hydroxy-L-proline provided the enantiomeric L-prolinol guanine derivative (36). Lastly, the 6-(dimethylamino)purine analogue, 37, was coupled to N-(benzyl-oxycarbonyl)-p-methoxy-L-phenylalanine to provide, after deprotection, the novel puromycin-like analogue 39. The analogues 26-29, 36, and 39 were all evaluated for antitumor and, except for 39, for antiviral activity. These compounds failed to appreciably inhibit the growth of P388 mouse leukemia cells in vitro at concentrations up to 100 micrograms/mL. In addition, they did not exhibit noticeable activity against the human immunodeficiency virus or herpes simplex virus type 1 at concentrations as high as 100 microM. The adenine analogue, 26, did, however, prove to be a substrate for adenosine deaminase. It possessed an affinity for the enzyme only 50% less than that of adenosine with a Ki = 85 microM.

Mechanism of inhibition of human immunodeficiency virus type 1 reverse transcriptase and human DNA polymerases alpha, beta, and gamma by the 5'-triphosphates of carbovir, 3'-azido-3'-deoxythymidine, 2',3'-dideoxyguanosine and 3'-deoxythymidine. A novel RNA template for the evaluation of antiretroviral drugs

Carbovir (the carbocyclic analog of 2'-3'-didehydro-2',3'-dideoxyguanosine) is a potent inhibitor of human immunodeficiency virus type 1 (HIV-1) replication. Assays were developed to assess the mechanism of inhibition by the 5'-triphosphate of carbovir of HIV-1 reverse transcriptase using either RNA or DNA templates that contain all four natural nucleotides. Carbovir-TP was a potent inhibitor of HIV-1 reverse transcriptase using either template with Ki values similar to that observed by AZT-TP, ddGTP, and ddTTP. The kinetic constants for incorporation of these nucleotide analogs into DNA by HIV-1 reverse transcriptase using either template were similar to the values seen for their respective natural nucleotides. In addition, the incorporation of either carbovir-TP or AZT-TP in the presence of dGTP or dTTP, respectively, indicated that the mechanism of inhibition by these two nucleotide analogs was due to their incorporation into the DNA resulting in chain termination. Carbovir-TP was not a potent inhibitor of DNA polymerase alpha, beta, or gamma, or DNA primase. Given the potent activity of carbovir-TP against HIV-1 reverse transcriptase and its lack of activity against human DNA polymerases, we believe that further evaluation of this compound as a potential drug for the treatment of HIV-1 infection is warranted.