Atropo-enantioselective synthesis of a simplified analog of mastigophorenes A and B

A first approach to the atroposelective total synthesis of mastigophorenes is described, the directed preparation of a structurally slightly modified analog of mastigophorenes A and B, with a tert-butyl instead of a substituted, chiral cyclopentyl residue. Its (partially protected) monomeric half is dimerized by oxidative (phenolic) coupling to give the corresponding biphenyl in a racemic form, or atropo-enantioselectively via the corresponding biaryl lactone, to give the M-or, optionally, the P-enantiomeric form, by stereoselective ring opening and subsequent standard transformations. (C) 1998 Elsevier Science Ltd. All rights reserved.