Issue in Honor of Prof. T. Govindachari ARKIVOC 2001 (viii) 146-153
Synthesis of cyclobutane fused .-butyro lactones through intramolecular [2+2] photocycloaddition. Application in a formal synthesis of grandisol
Jagannath Panda, Sarita Ghosh and Subrata Ghosh*
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta - 700 032, India E-mail:
[email protected]
Dedicated to Professor T. R. Govindachari on the occasion of his 85th birthday (received 02 May 01; accepted 15 Oct 01; published on the web 23 Oct 01)
Abstract
An approach to the synthesis of cyclobutane fused .-butyrolactones is described. The key step involves a Cu(I) catalysed intramolecular [2+2] photocycloaddition of 1,6-dienes in which the two alkene units are tethered through acetal oxygen. The resulting bicyclic lactols were then oxidised to provide the title compounds. The synthetic potential of these lactones is illustrated by a formal synthesis of grandisol.
Keywords: Cyclobutane fused butyrolactones, intramolecular, [2+2]photocycloaddition, bicyclic lactols, grandisol
Introduction
The cyclobutane ring is present in many naturally occurring molecules. Grandisol 1,1 the pheromone 2,2 hebellophyllene 33 and kelsoene 44 are a few representative examples. Cyclobutane derivatives are also extensively used as synthetic intermediates5 taking advantage of their inherent ring strain that renders them to undergo facile ring enlargement and ring cleavage. Thus development of methodologies for the synthesis of highly functionalised four membered rings is of continued interest.6 We envisaged that cyclobutane fused .-butyro lactones represented by the general structure 5 may lead to access to the natural products 1-4. We herein, report7 a general protocol for the synthesis of the cyclobutane fused .-butyro lactones and its application in a formal synthesis of grandisol 1.
ISSN 1424-6376 Page 146 ©ARKAT USA, Inc
