Divergent Synthesis of Novel Cylindrocyclophanes that Inhibit Methicillin-Resistant Staphylococcus aureus (MRSA)

The cylindrocyclophanes are a family of macrocyclic natural products reported to exhibit antibacterial activity. Little is known about the structural basis of this activity due to the challenges associated with their synthesis or isolation. We hypothesised that structural modification of the cylindrocyclophane scaffold could streamline their synthesis without significant loss of activity. Herein, we report a divergent synthesis of the cylindrocyclophane core enabling access to symmetrical macrocycles by means of a catalytic, domino cross-metathesis-ring-closing metathesis cascade, followed by late-stage diversification. Phenotypic screening identified several novel inhibitors of methicillin-resistant Staphylococcus aureus. The most potent inhibitor has a unique tetrabrominated [7,7]paracyclophane core with no known counterpart in nature. Together these illustrate the potential of divergent synthesis using catalysis and unbiased screening methods in modern antibacterial discovery.

C(sp3)-H arylation to construct all-syn cyclobutane-based heterobicyclic systems: a novel fragment collection

All-syn fused cyclobutanes remain an elusive chemotype and thus present an interesting synthetic challenge. Herein, we report the successful application of Pd-catalysed C(sp3)-H arylation of cyclobutane compounds to generate all-syn heterobicyclic fragments using an innovative 'inside-out' approach. Through this strategy we generate a virtual collection of 90 fragments, which we demonstrate to have enhanced three-dimensionality and superior fragment-like properties compared to existing collections.

Hydroxylated Rotenoids Selectively Inhibit the Proliferation of Prostate Cancer Cells

Prostate cancer is one of the leading causes of cancer-related death in men. The identification of new therapeutics to selectively target prostate cancer cells is therefore vital. Recently, the rotenoids rotenone (1) and deguelin (2) were reported to selectively kill prostate cancer cells, and the inhibition of mitochondrial complex I was established as essential to their mechanism of action. However, these hydrophobic rotenoids readily cross the blood-brain barrier and induce symptoms characteristic of Parkinson's disease in animals. Since hydroxylated derivatives of 1 and 2 are more hydrophilic and less likely to readily cross the blood-brain barrier, 29 natural and unnatural hydroxylated derivatives of 1 and 2 were synthesized for evaluation. The inhibitory potency (IC50) of each derivative against complex I was measured, and its hydrophobicity (Slog10P) predicted. Amorphigenin (3), dalpanol (4), dihydroamorphigenin (5), and amorphigenol (6) were selected and evaluated in cell-based assays using C4-2 and C4-2B prostate cancer cells alongside control PNT2 prostate cells. These rotenoids inhibit complex I in cells, decrease oxygen consumption, and selectively inhibit the proliferation of prostate cancer cells, leaving control cells unaffected. The greatest selectivity and antiproliferative effects were observed with 3 and 5. The data highlight these molecules as promising therapeutic candidates for further evaluation in prostate cancer models.

Demonstration of the utility of DOS-derived fragment libraries for rapid hit derivatisation in a multidirectional fashion

Organic synthesis underpins the evolution of weak fragment hits into potent lead compounds. Deficiencies within current screening collections often result in the requirement of significant synthetic investment to enable multidirectional fragment growth, limiting the efficiency of the hit evolution process. Diversity-oriented synthesis (DOS)-derived fragment libraries are constructed in an efficient and modular fashion and thus are well-suited to address this challenge. To demonstrate the effective nature of such libraries within fragment-based drug discovery, we herein describe the screening of a 40-member DOS library against three functionally distinct biological targets using X-Ray crystallography. Firstly, we demonstrate the importance for diversity in aiding hit identification with four fragment binders resulting from these efforts. Moreover, we also exemplify the ability to readily access a library of analogues from cheap commercially available materials, which ultimately enabled the exploration of a minimum of four synthetic vectors from each molecule. In total, 10-14 analogues of each hit were rapidly accessed in three to six synthetic steps. Thus, we showcase how DOS-derived fragment libraries enable efficient hit derivatisation and can be utilised to remove the synthetic limitations encountered in early stage fragment-based drug discovery.

Fsp3-rich and diverse fragments inspired by natural products as a collection to enhance fragment-based drug discovery

Herein, we describe the natural product inspired synthesis of 38 complex small molecules based upon 20 unique frameworks suitable for fragment-based screening. Utilising an efficient strategy, two key building block diastereomers were harnessed to generate novel, three-dimensional fragments which each possess numerous synthetically accessible fragment growth positions.

Recent Applications of Diversity-Oriented Synthesis Toward Novel, 3-Dimensional Fragment Collections

Fragment-based drug discovery (FBDD) is a well-established approach for the discovery of novel medicines, illustrated by the approval of two FBBD-derived drugs. This methodology is based on the utilization of small "fragment" molecules (<300 Da) as starting points for drug discovery and optimization. Organic synthesis has been identified as a significant obstacle in FBDD, however, in particular owing to the lack of novel 3-dimensional (3D) fragment collections that feature useful synthetic vectors for modification of hit compounds. Diversity-oriented synthesis (DOS) is a synthetic strategy that aims to efficiently produce compound collections with high levels of structural diversity and three-dimensionality and is therefore well-suited for the construction of novel fragment collections. This Mini-Review highlights recent studies at the intersection of DOS and FBDD aiming to produce novel libraries of diverse, polycyclic, fragment-like compounds, and their application in fragment-based screening projects.

Synthesis of Structurally Diverse N-Substituted Quaternary-Carbon-Containing Small Molecules from α,α-Disubstituted Propargyl Amino Esters

N-containing quaternary stereocenters represent important motifs in medicinal chemistry. However, due to their inherently sterically hindered nature, they remain underrepresented in small molecule screening collections. As such, the development of synthetic routes to generate small molecules that incorporate this particular feature are highly desirable. Herein, we describe the diversity-oriented synthesis (DOS) of a diverse collection of structurally distinct small molecules featuring this three-dimensional (3D) motif. The subsequent derivatisation and the stereoselective synthesis exemplified the versatility of this strategy for drug discovery and library enrichment. Chemoinformatic analysis revealed the enhanced sp3 character of the target library and demonstrated that it represents an attractive collection of biologically diverse small molecules with high scaffold diversity.

Diversity-oriented synthesis of heterocycles and macrocycles by controlled reactions of oxetanes with α-iminocarbenes

Using N-sulfonyl triazoles as substrates, compounds as diverse as 2-imino tetrahydrofurans, 13- and 15-membered ring aza-macrocycles can be prepared selectively via formal [1 + 4], [5 + 4 + 4] and [3 + 4 + 4 + 4] condensations of α-imino carbenes and oxetanes under Rh(ii)-catalysis or thermal activation. Spirocyclic N-heterocycles are also accessible by means of Buchwald-Hartwig and Pictet-Spengler cyclizations. By reaction control, substrate selection or further derivatization, a large variety of chemical structures is thus achievable. Finally, using triazoles reacting under thermal activation, interesting mechanistic insight was obtained.

Randomized, double-blind, multicenter comparison of oral cefditoren 200 or 400 mg BID with either cefuroxime 250 mg BID or cefadroxil 500 mg BID for the treatment of uncomplicated skin and skin-structure infections

BACKGROUND

Uncomplicated skin and skin-structure infections are commonly observed in medical practice. Because these infections typically are confined to the superficial layers and seldom lead to the destruction of skin structures and resultant systemic dissemination, in general they can be treated with an oral antibiotic with potent microbiologic activity against gram-positive pathogens.

OBJECTIVE

This paper compares the efficacy and tolerability of 3 beta-lactam antibiotics in patients with uncomplicated skin and skin-structure infections.

METHODS

Two double-blind, multicenter, parallel-group studies were conducted, in which patients aged > or = 12 years with uncomplicated skin and skin-structure infections were randomized to receive cefditoren 200 or 400 mg, cefuroxime 250 mg, or cefadroxil 500 mg, each BID for 10 days. Study 1 compared cefditoren with cefuroxime; Study 2 compared cefditoren with cefadroxil. Clinical and microbiologic responses were assessed at a posttreatment visit (within 48 hours of treatment completion) and test-of-cure visit (7-14 days after treatment completion). Patients were monitored closely throughout the study with the use of physical examinations, clinical laboratory tests, and assessment of adverse events.

RESULTS

A total of 1,685 patients (855 males, 830 females; mean age, 41.1 years [range, 12-95 years]) were enrolled. Within both studies, the 3 treatment groups were similar at baseline based on demographic characteristics and types of infection. Cellulitis (26%), wound infection (25%), and simple abscess (15%) were the most common infections. Clinical cure rates at the test-of-cure visit were 85% (443/523) for cefditoren 200 mg, 83% (427/516) for cefditoren 400 mg, 88% (234/265) for cefuroxime, and 85% (211/248) for cefadroxil. At the test-of-cure visit, cefditoren 200 mg had eradicated significantly fewer of the causative pathogens isolated before treatment in microbiologically evaluable patients than did cefuroxime in Study 1 (P = 0.043) but significantly more of the pathogens than did cefadroxil in Study 2 (P = 0.018). Eradication rates for the most commonly isolated pathogens were generally similar in the 3 treatment groups in both studies, with the only significant difference favoring cefditoren 200 and 400 mg over cefadroxil for Peptostreptococcus species in Study 2 (P = 0.016 and P = 0.003, respectively). A minority of patients (< or = 5% in any treatment group) discontinued study-drug treatment prematurely due to a treatment-related adverse event, with statistically higher rates for cefditoren 400 mg than for cefditoren 200 mg and the comparator cephalosporins (each P < 0.05). All 3 cephalosporins were generally well tolerated. Most adverse events (>93%) were categorized as mild to moderate, with the most common being diarrhea, nausea, and headache.

CONCLUSION

In this population of patients with uncomplicated skin and skin-structure infections, including those due to Staphylococcus aureus or Streptococcus pyogenes, the clinical cure rate and tolerability of cefditoren were comparable to those of cefuroxime and cefadroxil.

Dose-response relationship of lansoprazole to gastric acid antisecretory effects

BACKGROUND

Proton pump inhibitors have been found to be effective in numerous studies in patients with peptic ulcer disease, particularly associated with Helicobacter pylori and gastro-oesophogeal reflux disorders. Optimal healing rates of antisecretory therapy for peptic acid disease is dependent upon the degree and duration of acid suppression and the length of treatment.

OBJECTIVE

To evaluate the extent and duration of gastric acid suppression of several lansoprazole regimens, administered for 5 consecutive days in 32 healthy adult male subjects.

METHODS

Intragastric 24-h pH monitoring was performed in 32 healthy subjects in a randomized, double-blind, four-way crossover study. Sixteen subjects (Group 1) received lansoprazole 30 mg o.d. (once daily), 15 mg b.d. (twice daily), 30 mg b.d. and 30 mg t.d.s. (three times a day) for 5 days; and 16 subjects (Group 2) received lansoprazole 30 mg o.d., 60 mg o.d., 60 mg b.d. and 60 mg t.d.s. for 5 days.

RESULTS

Mean 24-h intragastric pH values for lansoprazole 30 mg o.d., 15 mg b.d., 30 mg b.d. and 30 mg t.d.s. were 4.47, 4.57, 5.07 and 5.63, respectively. Multiple-dose regimens of lansoprazole 30 mg b.d. and t.d.s. produced greater acid suppression compared to lansoprazole 30 mg o.d. and 15 mg b.d. There was no significant difference in acid suppression between lansoprazole 30 mg o.d. and 15 mg b.d. Mean 24-h intragastric pH values for lansoprazole 30 mg o.d., 60 mg o.d., 60 mg b.d. and 60 mg t.d.s. were 4.13, 4.45, 5.19 and 5.13, respectively. Multiple-dose regimens of lansoprazole 60 mg b.d. and t.d.s. produced significantly greater acid suppression compared to lansoprazole 30 mg o.d. and 60 mg o.d. There was no significant difference in acid suppression between lansoprazole 30 mg o.d. and 60 mg o.d. Lansoprazole 30 mg t.d.s., 60 mg b.d. and 60 mg t.d.s. produced significantly greater percentage time above pH 3, 4, 5 and 6 than did lansoprazole 30 mg o.d. Post-regimen serum gastrin values increased by 50-130% from pre-study mean values but remained within normal range and returned to pre-study values 7-14 days post-dosing.

CONCLUSIONS

Multiple-dose regimens of lansoprazole (> or =30 mg b.d. for 5 days) produce significantly increased intragastric pH and significantly longer duration of increased intragastric pH than does lansoprazole 30 mg administered once daily.