Synthesis Of Stable Analogues Research Articles

N-Heterocyclic Vinylidene-Stabilized Phosphorus Biradicaloid.

Four-membered biradicaloid compounds containing a N2 E2 (E=main group element) framework have been thoroughly investigated; however, the synthesis of stable analogues with a C2 P2 skeleton remains a challenge. Base-mediated double C-H functionalization of IPr=CH2 (1) (IPr=C[N(2,6-iPr2 -C6 H3 )CH]2 ) with PCl3 affords [{(IPr)CP}2 Cl]Cl (2) as a royal blue solid. Treatment of 2 with KC8 yields the stable phosphorus biradicaloid [(IPr)CP]2 (3) featuring a four-membered C2 P2 ring. Compound 3 is diamagnetic and shows sharp and temperature-independent NMR resonances, revealing its singlet biradicaloid nature. The stability of 3 is attributed to the σ- and π-electron-donating property of the N-heterocyclic vinylidene [(IPr)C] group.

Lipoxins Inhibit Akt/PKB Activation and Cell Cycle Progression in Human Mesangial Cells

Lipoxins (LX) are endogenously produced eicosanoids with a spectrum of bioactions that suggest anti-inflammatory, pro-resolution roles for these agents. Mesangial cell (MC) proliferation plays a pivotal role in the pathophysiology of glomerular inflammation and is coupled to sclerosis and tubulointerstitial fibrosis. We have previously reported that LXA4 acts through a specific G-protein-coupled-receptor (GPCR) to modulate MC proliferation in response to the proinflammatory mediators LTD4 and platelet-derived growth factor (PDGF). Further investigations revealed that these effects were mediated by modulation of receptor tyrosine kinase activity. Here we have explored the underlying mechanisms and report inhibition of growth factor (PDGF; epithelial growth factor) activation of Akt/PKB by LXA4. LXA4 (10 nmol/L) modulates PDGF-induced (10 ng/ml, 24 hours) decrements in the levels of cyclin kinase inhibitors p21Cip1 and p27Kip1. PDGF-induced increases in CDK2-cyclin E complex formation are also inhibited by LXA4. The potential of LXA4 as an anti-inflammatory therapeutic is compromised by its degradation; this has been circumvented by synthesis of stable analogs. We report that 15-(R/S)-methyl-LXA4 and 16-phenoxy-LXA4 mimic the native compound with respect to modulation of cell proliferation and PDGF-induced changes in cell cycle proteins. In vivo, MC proliferation in response to PDGF is associated with TGFbeta1 production and the subsequent development of renal fibrosis. Here we demonstrate that prolonged (24 to 48 hours) exposure to PDGF is associated with autocrine TGFbeta1 production, which is significantly reduced by LXA4. In aggregate these data demonstrate that LX inhibit PDGF stimulated proliferation via modulation of the PI-3-kinase pathway preventing mitogen-elicited G1-S phase progression and suggest the therapeutic potential of LX as anti-fibrotic agents.

Prostanoids for pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a severe condition that markedly reduces exercise capacity and survival in the affected patient population. PAH includes primary pulmonary hypertension (PPH) and pulmonary hypertension associated with collagen vascular diseases, congenital systemic-to-pulmonary shunts, portal hypertension and HIV infection. All these conditions share virtually identical obstructive pathologic changes of the pulmonary microcirculation and probably similar pathobiologic processes. The pathophysiology is characterized by a progressive increase in pulmonary vascular resistance, leading to right ventricular failure and death. Prostacyclin is an endogenous substance that is produced by vascular endothelial cells and induces vasodilatation, inhibition of platelet activity, and antiproliferative effects. A dysregulation of prostacyclin metabolic pathways has been shown in patients with PAH and this represents the rationale for the exogenous therapeutic administration of this substance. The clinical use of prostacyclin in patients with PAH has been made possible by the synthesis of stable analogs that possess different pharmacokinetic properties but share similar pharmacodynamic effects. Experience in humans has been initially collected with epoprostenol, which is a synthetic salt of prostacyclin. Epoprostenol has a short half-life in the circulation and requires continuous administration by the intravenous route by means of infusion pumps and permanent tunnelized catheters. In addition, epoprostenol is unstable at room temperature, and the complex delivery system required is associated with several adverse effects and potentially serious complications. For these reasons, alternatives to intravenous epoprostenol have been sought and this has led to the development of analogs that can be administered subcutaneously (treprostinil), orally (beraprost sodium) or by inhalation (iloprost). Three unblinded clinical trials and several uncontrolled trials have shown that treatment with epoprostenol improved symptoms and exercise capacity in New York Heart Association (NYHA) class III and IV PAH patients and also survival in patients with PPH. Subcutaneous treprostinil improved symptoms, exercise, hemodynamics and clinical events in the largest clinical trial ever performed in PAH, but local infusion site reactions limited efficacy in a proportion of patients. Oral beraprost sodium improved exercise capacity only in patients with PPH and is the only prostacyclin analog that has also been tested in NYHA class II patients. Inhaled iloprost has improved symptoms, exercise capacity and clinical events in patients with PAH and inoperable chronic thromboembolic pulmonary hypertension. The favorable effects of prostanoids observed in all studies coupled with different profiles of adverse events and tolerability for each prostacyclin analog allow the unique opportunity to select the most appropriate compound for the individual patient with PAH.

MEDICAL THERAPY OF PULMONARY HYPERTENSION: The Prostacyclins

Prostacyclin is a substance produced by endothelial cells that induces vasodilation and inhibition of platelet aggregation and of vascular cell migration and proliferation. A dysregulation of the prostacyclin metabolic pathways has been shown in patients with pulmonary arterial hypertension. The clinical use of prostacyclin has been made possible by the synthesis of stable analogues that possesses different pharmacokinetic properties but share similar pharmacodynamic effects. The greatest experience has been collected with intravenous epoprostenol while other compounds like subcutaneous UT-15, inhaled iloprost and oral beraprost are currently in different stages of clinical development. Although favorable results have been reported for each compound, different benefit-to-side effects profiles characterize the various modalities of the administration.

Synthesis of stable analogs in blood and conformational analysis of arenastatin A, a potent cytotoxic spongean depsipeptide

In order to produce stable analogs in blood of arenastatin A, a potent cytotoxic depsipeptide from the marine sponge Dysidea arenaria, we synthesized four analogs in which the 15-20 ester linkage was modified. Among them, the carba analog and 20-deoxo analog showed stability in serum. The conformation of arenastatin A and its three analogs were analyzed by distance-restrained molecular dynamic calculation to elucidate a three-dimensional stereostructure contributing to the extremely potent cytotoxicity of arenastatin A.

Synthesis of Stable Analogues of Glyceroglycolipids

Abstract Stable C-glycosidic analogues of 2-O-(β-D-glucopyranosyl)-sn-glycerol (1a), 2-O-(β-D-galactopyranosyl)-sn-glycerol (1b), 1-O-(β-D-glucopyranosyl)-sn-glycerol (7) and their dipalmitoyl ester have been synthesised starting from the corresponding 2,3,4,6-tetra-O-benzyl-glyconolactones 9. The 2-O-derivatives 1 were obtained by methylenation of the lactone 9, reaction of the obtained glycoexoenitol 10 with a malonyl radical, reduction of the malonyl derivative 11 and deprotection. The 1-O-derivative 7 was obtained by reaction of the lactone 9 with butenylmagnesium bromide, reduction of the obtained lactol 14, osmylation and deprotection. © 1997 Elsevier Science Ltd.