Stereoselective synthesis of (R)-(−) and (S)-(+)-phoracantholide I from (R)-(+)-γ-valerolactone
摘要:
A concise total synthesis of (R)-(-)-phoracantholide I 1 and (S)-(+)-phoracantholide I 2 has been developed from (R)-(+)-gamma-valerolactone 6. The key steps in the synthesis of these macrolides involved enzymatic reduction of Levulinic ester 4 by asymmetric dehydrogenase, Z-selective Wittig reaction of (4-carboxybutyl)triphenylphosphonium ylide 11 with lactol 7, and cyclization of seco-acid 8 using either a Yamaguchi lactonization protocol or a Mitsunobu protocol to afford (R)-(-)-phoracantholide I and (S)-(+)-phoracantholide I respectively. (C) 2016 Elsevier Ltd. All rights reserved.
A short and efficient synthesis of (+)-spirolaxine methylether, a metabolite of the fungus Sporotrichum laxum with inhibitory activity against Helicobacter pylori, is described. The synthesis has been carried out by a Prins cyclization, to obtain the [6,5]-spiroketal system, and a Wadsworth−Emmons condensation, applied for the installation of the polymethylene chain on the phthalide moiety.
(S)-(+)-Sulcatol (1) and its antipode (1′) were synthesized from (R)-(−)-glutamic acid (2), and its antipode (2′), respectively. This established the absolute configurations of both enantiomers of sulcatol and afforded key materials to study the relationship between pheromone activity and chirality.
The formalsynthesis of Cladospolide-C and its analog is achieved by using enantiopure (R)-γ–valerolactone 10. The significant points of this synthesis are the stereoselective dihydroxylation of α, β-unsaturated ester 16 using Sharpless protocol, Wittig olefination of γ –valerolactol 6 with triphenylphosphonium iodide salt 7, one pot selective oxidation of 22 and subsequent C2-homologation with good