Crystal structure of (1rs, 14sr, 17rs, 18rs)-2,20-dioxa-17-methyltricyclo [16,3,0 1,14,0 1,18] heneicosa-15-ene-3,19,21-trione; a macrocyclic lac

Abstract

An X-ray study of the major product of the intramolecular Diels-Alder reaction of the diene-anhydride ( 2) has confirmed it as being the desired cytochalasan analogue ( 3). In particular the cyclisation has been regioselective, and has taken place via the endo transition state to generate the adduct with the correct relative configurations at the four chiral centres. Details of the conformational geometry of ( 3) are discussed.