The ubiquitous phosphoinositides

Development of the telescoped flow Pd-catalyzed aerobic alcohol oxidation/reductive amination sequence in the synthesis of new phosphatidylinositide 3-kinase inhibitor (CPL302415)

Herein, we describe a two-step sequential flow synthesis: Pd-catalyzed aerobic oxidation to an aldehyde 2, which is then converted by reductive amination in H-Cube® PRO into CPL302415 (3). CPL302415 is our new PI3Kδ inhibitor, which is now under evaluation for the treatment of systemic lupus erythematosus. The process was optimized using the DoE approach and generalized to other biologically active derivatives of CPL302415.

Discovery of Pyrazolo[1,5-a]pyrimidine derivative as a potent and selective PI3Kγ/δ dual inhibitor

Phosphoinositol 3-kinases (PI3Ks) γ and δ are primarily expressed in leukocytes and play crucial roles in regulation of the immune system. Dual inhibition of PI3Kγ/δ has emerged as an effective approach to regulate the tumor microenvironment. Here, we report the exploration of structure-activity relationship optimization which led to the discovery of a potent PI3Kγ/δ dual inhibitor 15u (IHMT-PI3K-455). 15u exhibits strong potency in biochemical and cellular assays and it repolarizes M2 phenotype toward M1 phenotype in THP-1 and BMDM macrophages. In addition, it shows suitable in vivo properties as demonstrated through pharmacokinetic studies in rats and pharmacodynamics properties in a MC38 xenograft model.

The design of experiments (DoE) in optimization of an aerobic flow Pd-catalyzed oxidation of alcohol towards an important aldehyde precursor in the synthesis of phosphatidylinositide 3-kinase inhibitor (CPL302415)

Herein, we describe the development of a green, scalable flow Pd-catalyzed aerobic oxidation for the key step in the synthesis of CPL302415, which is a new PI3Kδ inhibitor. Applying this environmental-friendly, sustainable catalytic oxidation we significantly increased product yield (up to 84%) and by eliminating of workup step, we improved the waste index and E factor (up to 0.13) in comparison with the stoichiometric synthesis. The process was optimized by using the DoE approach.

Design, Synthesis, and Development of Pyrazolo[1,5-a]pyrimidine Derivatives as a Novel Series of Selective PI3Kδ Inhibitors: Part II—Benzimidazole Derivatives

Phosphoinositide 3-kinase (PI3K) is the family of lipid kinases participating in vital cellular processes such as cell proliferation, growth, migration, or cytokines production. Due to the high expression of these proteins in many human cells and their involvement in metabolism regulation, normal embryogenesis, or maintaining glucose homeostasis, the inhibition of PI3K (especially the first class which contains four subunits: α, β, γ, δ) is considered to be a promising therapeutic strategy for the treatment of inflammatory and autoimmune diseases such as systemic lupus erythematosus (SLE) or multiple sclerosis. In this work, we synthesized a library of benzimidazole derivatives of pyrazolo[1,5-a]pyrimidine representing a collection of new, potent, active, and selective inhibitors of PI3Kδ, displaying IC50 values ranging from 1.892 to 0.018 μM. Among all compounds obtained, CPL302415 (6) showed the highest activity (IC50 value of 18 nM for PI3Kδ), good selectivity (for PI3Kδ relative to other PI3K isoforms: PI3Kα/δ = 79; PI3Kβ/δ = 1415; PI3Kγ/δ = 939), and promising physicochemical properties. As a lead compound synthesized on a relatively large scale, this structure is considered a potential future candidate for clinical trials in SLE treatment.

Lipid transfer proteins and instructive regulation of lipid kinase activities: Implications for inositol lipid signaling and disease

Cellular membranes are critical platforms for intracellular signaling that involve complex interfaces between lipids and proteins, and a web of interactions between a multitude of lipid metabolic pathways. Membrane lipids impart structural and functional information in this regulatory circuit that encompass biophysical parameters such as membrane thickness and fluidity, as well as chaperoning the interactions of protein binding partners. Phosphatidylinositol and its phosphorylated derivatives, the phosphoinositides, play key roles in intracellular membrane signaling, and these involvements are translated into an impressively diverse set of biological outcomes. The phosphatidylinositol transfer proteins (PITPs) are key regulators of phosphoinositide signaling. Found in a diverse array of organisms from plants, yeast and apicomplexan parasites to mammals, PITPs were initially proposed to be simple transporters of lipids between intracellular membranes. It now appears increasingly unlikely that the soluble versions of these proteins perform such functions within the cell. Rather, these serve to facilitate the activity of intrinsically biologically insufficient inositol lipid kinases and, in so doing, promote diversification of the biological outcomes of phosphoinositide signaling. The central engine for execution of such functions is the lipid exchange cycle that is a fundamental property of PITPs. How PITPs execute lipid exchange remains very poorly understood. Molecular dynamics simulation approaches are now providing the first atomistic insights into how PITPs, and potentially other lipid-exchange/transfer proteins, operate.

Conformationally restricted quinazolone derivatives as PI3Kδ-selective inhibitors: the design, synthesis and biological evaluation

A series of structurally novel quinazolone-based PI3Kδ-selective inhibitors were designed and synthesized via the approach of conformational restriction. The majority of them exhibited two-digit to single-digit nanomolar IC50 values against PI3Kδ, along with low micromolar to submicromolar GI50 values against human malignant B-cell line SU-DHL-6. The representative compound, with the most potent PI3Kδ inhibitory activity (IC50 = 6.3 nM) and anti-proliferative activity (GI50 = 0.21 μM) in this series, was further evaluated for its PI3Kδ selectivity, capability to down-regulate PI3K signaling in SU-DHL-6 cells, in vitro metabolic stability, and pharmacokinetic (PK) properties. The experimental results illustrated that this compound, as a promising lead, merits extensive structural optimization for exploring novel PI3Kδ-selective inhibitors as clinical candidates.

Discovery and in Vivo Evaluation of the Potent and Selective PI3Kδ Inhibitors 2-((1S)-1-((6-Amino-5-cyano-4-pyrimidinyl)amino)ethyl)-6-fluoro-N-methyl-3-(2-pyridinyl)-4-quinolinecarboxamide (AM-0687) and 2-((1S)-1-((6-Amino-5-cyano-4-pyrimidinyl)amino)ethyl)-5-fluoro-N-methyl-3-(2-pyridinyl)-4-quinolinecarboxamide (AM-1430)

Optimization of the potency and pharmacokinetic profile of 2,3,4-trisubstituted quinoline, 4, led to the discovery of two potent, selective, and orally bioavailable PI3Kδ inhibitors, 6a (AM-0687) and 7 (AM-1430). On the basis of their improved profile, these analogs were selected for in vivo pharmacodynamic (PD) and efficacy experiments in animal models of inflammation. The in vivo PD studies, which were carried out in a mouse pAKT inhibition animal model, confirmed the observed potency of 6a and 7 in biochemical and cellular assays. Efficacy experiments in a keyhole limpet hemocyanin model in rats demonstrated that administration of either 6a or 7 resulted in a strong dose-dependent reduction of IgG and IgM specific antibodies. The excellent in vitro and in vivo profiles of these analogs make them suitable for further development.

Analysis of the membrane proteome of ciprofloxacin-resistant macrophages by stable isotope labeling with amino acids in cell culture (SILAC)

Overexpression of multidrug transporters is a well-established mechanism of resistance to chemotherapy, but other changes may be co-selected upon exposure to drugs that contribute to resistance. Using a model of J774 macrophages made resistant to the fluoroquinolone antibiotic ciprofloxacin and comparing it with the wild-type parent cell line, we performed a quantitative proteomic analysis using the stable isotope labeling with amino acids in cell culture technology coupled with liquid chromatography electrospray ionization Fourier transform tandem mass spectrometry (LC-ESI-FT-MS/MS) on 2 samples enriched in membrane proteins (fractions F1 and F2 collected from discontinuous sucrose gradient). Nine hundred proteins were identified with at least 3 unique peptides in these 2 pooled fractions among which 61 (F1) and 69 (F2) showed a significantly modified abundance among the 2 cell lines. The multidrug resistance associated protein Abcc4, known as the ciprofloxacin efflux transporter in these cells, was the most upregulated, together with Dnajc3, a protein encoded by a gene located downstream of Abcc4. The other modulated proteins are involved in transport functions, cell adhesion and cytoskeleton organization, immune response, signal transduction, and metabolism. This indicates that the antibiotic ciprofloxacin is able to trigger a pleiotropic adaptative response in macrophages that includes the overexpression of its efflux transporter.

Measurement of phosphoinositide 3-kinase products in cultured Mammalian cells by HPLC

The phosphoinositide 3-kinase (PI3K) family catalyses the addition of a phosphate group to the D-3 position of polyphosphoinositides (PPIn). Since the discovery in the late 80s that phosphatidylinositol is phosphorylated in the D-3 position in eukaryotic cells, there has been an explosion of interest in these PPIn. Although the four D-3 PPIn (phosphatidylinositol 3-phophate (PtdIns3P), PtdIns(3,4)P(2), PtdIns(3,5)P(2), and PtdIns(3,4,5)P(3)) represent only a small proportion of PPIn, production of D-3 PPIn is required for an ever-increasing number of processes. Measurement of the PPIn levels in intact cells cultured cells has been vital to our understanding of the metabolism and function of these important signalling molecules; methods are described herein that allow measurement of PPIn levels in cultured cells, with emphasis on the 3-OH PPIn.

Elucidation of the fragmentation pathways of different phosphatidylinositol phosphate species (PIPx) using IRMPD implemented on a FT-ICR MS

This work reports on the fragmentation of phosphoinositides by tandem mass spectrometry (MS/MS) and MS³ experiments on a hybrid apex-Qe Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS) using internal infrared multiphoton dissociation (IRMPD). The fragmentation behavior of diacylphophatidylinositol triphosphate was intensively studied since an abundant loss of inositol biphosphate was observed. This loss was suggested to occur via phosphate migration along the inositol head group. Substantiation by MS³ experiments showed that this neutral loss is formed after the loss of water from the precursor ion, indicating phosphate migration along the inositol ring to the glycerol backbone. Further fragmentation of the ion formed by the loss of inositol biphosphate from diacylphophatidylinositol triphosphate resulted in the formation of a product ion with a molecular formula of C(3)H(5)O(7)P(2), corresponding to a glycerol backbone linked to two phosphate groups. We suggested different structures for this ion and compared their stability using modeling experiments.

Synthesis of 4-C-alkyl inositol 1,4,5-trisphosphates and 1,3,4,5-tetrakisphosphates

The preparation of 2,3,6-O-tribenzyl- and 2,6-O-dibenzyl-myo-inositols with beta-primary, secondary, and tertiary 4-C-alkyl or aryl groups is reported. Five of these novel polyols are elaborated to 4-C-alkyl Ins(1,4,5)P(3) and Ins(1,3,4,5)P(4) analogues. Regio- and stereoselective introduction of 4-C-alkyl or aryl substituents proceeded via a 4-exo-methylene oxide. Subsequent regioselective reduction of an orthobenzoate provided a divergent method to access both InsP(3) and InsP(4) precursors. Previously unreported phosphorylation of the tertiary hydroxyl and global deprotection afforded novel analogues that retain their full complement of polar and charged binding features.

Measurement of polyphosphoinositides in cultured mammalian cells

The seven phosphorylated derivatives of phosphatidylinositol (PtdIns), often collectively referred to as polyphosphoinositides (PPIn), are a minor component of eukaryotic cell membranes. Nevertheless, their synthesis is needed for an ever-increasing spectrum of cellular processes, including regulation of the actin cytoskeleton, chemotaxis, membrane trafficking, glucose uptake, and organelle acidification. PPIn metabolism is regulated dynamically by a network of kinases and phosphatases. Furthermore, synthesis of PPIn can be provoked by external stimuli; for example, the second messenger phosphatidylinositol 3,4,5-trisphosphate rapidly and transiently accumulates in cells challenged with agonists such as PDGF that activate receptor tyrosine kinases. The measurement of PPIn levels in in vivo cultured cells has been vital to our understanding of the metabolism and function of these important signaling molecules; methods are described herein that allow measurement of PPIn levels in culture cells in vivo.

Phosphoinositide signalling and cardiac arrhythmias

Arrhythmias arise from a complex interaction between structural changes in the myocardium and changes in cellular electrophysiology. Electrophysiological balance requires precise control of sarcolemmal ion channels and exchangers, many of which are regulated by phospholipid, phosphatidylinositol(4,5)bisphosphate. Phosphatidylinositol(4,5)bisphosphate is the immediate precursor of inositol(1,4,5)trisphosphate, a regulator of intracellular Ca2+ signalling and, therefore, a potential contributor to arrhythmogenesis by altering Ca2+ homeostasis. The aim of the present review is to outline current evidence that this signalling pathway can be a player in the initiation or maintenance of arrhythmias.

A selective PIKfyve inhibitor blocks PtdIns(3,5)P(2) production and disrupts endomembrane transport and retroviral budding

Phosphoinositides have crucial roles in cellular controls, many of which have been established through the use of small-molecule inhibitors. Here, we describe YM201636, a potent inhibitor of the mammalian class III phosphatidylinositol phosphate kinase PIKfyve, which synthesizes phosphatidylinositol 3,5-bisphosphate. Acute treatment of cells with YM201636 shows that the PIKfyve pathway is involved in the sorting of endosomal transport, with inhibition leading to the accumulation of a late endosomal compartment and blockade of retroviral exit. Inhibitor specificity is shown by the use of short interfering RNA against the target, as well as by rescue with the drug-resistant yeast orthologue Fab1. We concluded that the phosphatidylinositol 3,5-bisphosphate pathway is integral to endosome formation, determining morphology and cargo flux.

GxcDD, a putative RacGEF, is involved in Dictyostelium development

Background

Rho subfamily GTPases are implicated in a large number of actin-related processes. They shuttle from an inactive GDP-bound form to an active GTP-bound form. This reaction is catalysed by Guanine nucleotide exchange factor (GEFs). GTPase activating proteins (GAPs) help the GTPase return to the inactive GDP-bound form. The social amoeba Dictyostelium discoideum lacks a Rho or Cdc42 ortholog but has several Rac related GTPases. Compared to our understanding of the downstream effects of Racs our understanding of upstream mechanisms that activate Rac GTPases is relatively poor.

Results

We report on GxcDD (Guanine exchange factor for Rac GTPases), a Dictyostelium RacGEF. GxcDD is a 180-kDa multidomain protein containing a type 3 CH domain, two IQ motifs, three PH domains, a RhoGEF domain and an ArfGAP domain. Inactivation of the gene results in defective streaming during development under different conditions and a delay in developmental timing. The characterization of single domains revealed that the CH domain of GxcDD functions as a membrane association domain, the RhoGEF domain can physically interact with a subset of Rac GTPases, and the ArfGAP-PH tandem accumulates in cortical regions of the cell and on phagosomes. Our results also suggest that a conformational change may be required for activation of GxcDD, which would be important for its downstream signaling.

Conclusion

The data indicate that GxcDD is involved in proper streaming and development. We propose that GxcDD is not only a component of the Rac signaling pathway in Dictyostelium, but is also involved in integrating different signals. We provide evidence for a Calponin Homology domain acting as a membrane association domain. GxcDD can bind to several Rac GTPases, but its function as a nucleotide exchange factor needs to be studied further.

Synthesis and function of membrane phosphoinositides in budding yeast, Saccharomyces cerevisiae

It is now well appreciated that derivatives of phosphatidylinositol (PtdIns) are key regulators of many cellular processes in eukaryotes. Of particular interest are phosphoinositides (mono- and polyphosphorylated adducts to the inositol ring in PtdIns), which are located at the cytoplasmic face of cellular membranes. Phosphoinositides serve both a structural and a signaling role via their recruitment of proteins that contain phosphoinositide-binding domains. Phosphoinositides also have a role as precursors of several types of second messengers for certain intracellular signaling pathways. Realization of the importance of phosphoinositides has brought increased attention to characterization of the enzymes that regulate their synthesis, interconversion, and turnover. Here we review the current state of our knowledge about the properties and regulation of the ATP-dependent lipid kinases responsible for synthesis of phosphoinositides and also the additional temporal and spatial controls exerted by the phosphatases and a phospholipase that act on phosphoinositides in yeast.

Phosphoinositide regulation of neuroexocytosis: adding to the complexity

Exocytosis of neurotransmitter containing vesicles supports neuronal communication. The importance of molecular interactions involving specific lipids has become progressively more evident and the lipid composition of both the synaptic vesicle and the pre-synaptic plasma membrane at the active zone has significant functional consequences for neurotransmitter release. Several classes of lipids have been implicated in exocytosis including polyunsaturated fatty acids and phosphoinositides. This minireview will focus on recent developments regarding the role of phosphoinositides in neurosecretion.

Kanamycin alters cytoplasmic and nuclear phosphoinositide signaling in the organ of Corti in vivo

Aminoglycoside antibiotics strongly bind to phosphoinositides and affect their membrane distribution and metabolism. Kanamycin treatment also disrupts Rac/Rho signaling pathways to the actin cytoskeleton in the mouse inner ear in vivo. Here, we investigate the influence of kanamycin on phosphoinositide signaling in sensory cells (hair cells) of the mouse cochlea. Immunoreactivity to phosphatidylinositol-3,4,5-trisphosphate (PIP3) decreased in the organ of Corti, especially in outer hair cells, after 3-7 days of drug treatment, whereas imunoreactivity to phosphatidylinositol-4,5-bisphosphate (PIP2) increased. Immunoreactivity to PIP2 was present at the apical poles of outer hair cells, but appeared in their nuclei only after drug treatment. Furthermore, nuclear PIP2 formed a complex with histone H3 and attenuated its acetylation in outer hair cells. In agreement with reduced PIP3 signaling, phosphorylated Akt decreased in both the cytoplasm and nuclei of outer hair cells after kanamycin treatment. This study suggests that kanamycin disturbs the balance between PIP2 and PIP3, modifies gene transcription via histone acetylation and diminishes the PI3K/Akt survival pathway. These actions may contribute to the death of outer hair cells, which is a consequence of chronic kanamycin treatment.

Analysis of intact phosphoinositides in biological samples

It is now apparent that each of the known, naturally occurring polyphosphoinositides, the phosphatidylinositol monophosphates (PtdIns3P, PtdIns4P, PtdIns5P), phosphatidylinositol bisphosphates [PtdIns(3,4)P(2), PtdIns(3,5)P(2), PtdIns(4,5)P(2)], and phosphatidylinositol trisphosphate [PtdIns(3,4,5)P(3)], have distinct roles in regulating many cellular events, including intracellular signaling, migration, and vesicular trafficking. Traditional identification techniques require [(32)P]inorganic phosphate or [(3)H]inositol radiolabeling, acidified lipid extraction, deacylation, and ion-exchange head group separation, which are time-consuming and not suitable for samples in which radiolabeling is impractical, thus greatly restricting the study of these lipids in many physiologically relevant systems. Thus, we have developed a novel, high-efficiency, buffered citrate extraction methodology to minimize acid-induced phosphoinositide degradation, together with a high-sensitivity liquid chromatography-mass spectrometry (LC-MS) protocol using an acetonitrile-chloroform-methanol-water-ethylamine gradient with a microbore silica column that enables the identification and quantification of all phosphoinositides in a sample. The liquid chromatograph is sufficient to resolve PtdInsP(3) and PtdInsP(2) regioisomers; however, the PtdInsP regioisomers require a combination of LC and diagnostic fragmentation to MS(3). Data are presented using this approach for the analysis of phosphoinositides in human platelet and yeast samples.

Weak acid and alkali stress regulate phosphatidylinositol bisphosphate synthesis in Saccharomyces cerevisiae

Weak organic acids are used as food preservatives to inhibit the growth of spoilage yeasts, including Saccharomyces cerevisiae. Long-term adaptation to weak acids requires the increased expression of the ATP-binding cassette transporter Pdr12p, which catalyses the active efflux of the weak acids from the cytosol; however, very little is known about the signalling events immediately following application of weak acid stress. We have investigated the effects of weak acids on two stress-responsive signalling molecules, PtdIns(3,5)P2 and PtdIns(4,5)P2, which in S. cerevisiae are synthesized by Fab1p and Mss4p respectively. At low extracellular pH, benzoic acid, sorbic acid and acetic acid all cause a transient reduction in PtdIns(3,5)P2 accumulation and a more persistent rise in PtdIns(4,5)P2 levels. The increase in PtdIns(4,5)P2 levels is accompanied by a reorganization of the actin cytoskeleton. However, changes in PtdInsP2 levels are independent of weak acid-induced Pdr12p expression. In contrast, changing the extracellular medium to alkaline pH provokes a prolonged and substantial rise in PtdIns(3,5)P2 levels. As PtdIns(3,5)P2 synthesis is required for correct vacuole acidification, it is possible that levels of this molecule are modulated to maintain intracellular pH homoeostasis in response to weak acid and alkali stresses. In conclusion, we have expanded the repertoire of stress responses that affect PtdInsP2 levels to include weak acid and alkali stresses.

Regulation of type II PIP kinase by PKD phosphorylation

The type II PIP kinases phosphorylate the poorly understood inositol lipid PtdIns5P, producing the multi-functional lipid product PtdIns(4,5)P(2). To investigate the regulation of these enzymes by phosphorylation, we partially purified a protein kinase from pig platelets that phosphorylated type IIalpha PIP kinase on an activation loop threonine residue, T376. Pharmacological studies suggested this protein kinase was protein kinase D (PKD), and in vitro experiments confirmed this identification. A phospho-specific antibody was developed and used to demonstrate phosphorylation of T376 in living cells, and its enhancement under conditions in which PKD was activated. Although we were unable to determine the effects of phosphorylation on PIP kinase activity directly, mutation of T376 to aspartate significantly inhibited enzyme activity. We conclude that the type II PIP kinases are physiological targets for PKD phosphorylation, and that this modification is likely to regulate inositol lipid turnover by inhibition of these lipid kinases.

Identification of mitogen-activated protein kinase docking sites in enzymes that metabolize phosphatidylinositols and inositol phosphates

BACKGROUND

Reversible interactions between the components of cellular signaling pathways allow for the formation and dissociation of multimolecular complexes with spatial and temporal resolution and, thus, are an important means of integrating multiple signals into a coordinated cellular response. Several mechanisms that underlie these interactions have been identified, including the recognition of specific docking sites, termed a D-domain and FXFP motif, on proteins that bind mitogen-activated protein kinases (MAPKs). We recently found that phosphatidylinositol-specific phospholipase C-gamma1 (PLC-gamma1) directly binds to extracellular signal-regulated kinase 2 (ERK2), a MAPK, via a D-domain-dependent mechanism. In addition, we identified D-domain sequences in several other PLC isozymes. In the present studies we sought to determine whether MAPK docking sequences could be recognized in other enzymes that metabolize phosphatidylinositols (PIs), as well as in enzymes that metabolize inositol phosphates (IPs).

RESULTS

We found that several, but not all, of these enzymes contain identifiable D-domain sequences. Further, we found a high degree of conservation of these sequences and their location in human and mouse proteins; notable exceptions were PI 3-kinase C2-gamma, PI 4-kinase type IIbeta, and inositol polyphosphate 1-phosphatase.

CONCLUSION

The results indicate that there may be extensive crosstalk between MAPK signaling and signaling pathways that are regulated by cellular levels of PIs or IPs.

Membrane-lipid therapy: a new approach in molecular medicine

Although most drugs bind to proteins and regulate their activity, some drugs act through a new therapeutic approach called membrane-lipid therapy and bind to lipids, thus modulating the structure of membranes. Most cellular functions are highly dependent on the lipid environment because they are controlled by proteins in or around membranes. The wide variety of cell and organelle membranes and the existence of special lipid regions (e.g. microvilli) and domains (e.g. lipid rafts) support the possibility of designing specific lipid therapies. Indeed, recent evidence suggests that lipid therapy might have potential for the treatment of cancer, cardiovascular pathologies, neurodegenerative processes, obesity, metabolic disorders, inflammation, and infectious and autoimmune diseases.

Lipid links to better bone: a hypothesis

The combined resorptive activity of osteoclasts and the bone-generating function of osteoblasts result in the constant renewal of this vital tissue. It has long been appreciated that the coupled degradation and formation of bone is coordinately regulated by a complex interplay between endocrine and paracrine effectors; a recent report by now documents the possibility that cannabinoid receptors may also impact bone mass.

Polymer-bound oxathiaphospholane: a solid-phase reagent for regioselective monothiophosphorylation and monophosphorylation of unprotected nucleosides and carbohydrates

Two polymers bound to N,N-diisopropylamino-1,3,2-oxathiaphospholane were reacted with unprotected carbohydrates and nucleosides in the presence of 1H-tetrazole, followed by oxidation with tert-butyl hydroperoxide or sulfurization with Beaucage's reagent. The 1,3,2-oxathiaphospholane ring-opening with 3-hydroxypropionitrile, followed by treatment with DBU, afforded the corresponding monophosphate and monothiophosphate derivatives, respectively, through the elimination of polymer-bound ethylene episulfide. Reactions using this strategy offer the advantages of high regioselectivity, monosubstitution, and facile isolation and recovery of products.