Studies on the total synthesis of halicholactone and neohalicholactone: a stereoselective synthesis of C1-C13 fragment

Debendra K Mohapatra,Kulbhushan A Durugkar

doi:10.3998/ark.5550190.0005.114

Abstract

A stereoselective synthesis of C1-C13 fragment of halicholactone (1a) and neohalicholactone (1b) starting from (R)-isopropylidene glyceraldehyde is described. Key transformations include Simmons-Smith cyclopropanation, stereoselective reduction, ring-closing metathesis (RCM).

Highlights

Discovery in early 1960 that the marine coral Plexaura homomalla produces enormous quantities of prostaglandins1 initiated a fascinating era in the field of natural products chemistry
Interest on the part of chemists have been two fold, natural product chemists have investigated marine organisms as source of the new and unusual molecules, while synthetic organic chemists have followed by targeting these novel structures for development of new analogues and new synthetic methodologies and strategies
It is likely that the halicholactone originates from transformation analogous to those represented for the constanolactones except initiated through a 15-lipoxygenase introduced hydroperoxide

Summary

Introduction

Discovery in early 1960 that the marine coral Plexaura homomalla produces enormous quantities of prostaglandins1 initiated a fascinating era in the field of natural products chemistry. From the retrosynthetic analysis of halicholactone (1a) and neohalicholactone (1b) (Scheme 1), the (R)-2, 3-O-isopropylidene glyceraldehyde [8] was chosen as suitable starting material which was converted to cyclopropyl carboxaldehyde 7 following the method reported by us.5 Subsequent addition of aldehyde 7 to allylmagnesium bromide in ether provided the homoallyl alcohol 6 and 6a as 1:1 diastereomeric mixture in 89% yield, separable with difficulty by repeated column chromatography.

Results

Conclusion