C2-symmetric enantiopure bis-α,β-butenolides as diastereoselective substrates in ethylene photocycloaddition
摘要:
Several C-2-symmetric bis-alpha,beta-butenolides have been synthesised starting from D-mannitol. Their [2+2]-photocycloaddition to ethylene has been studied as a model reaction to evaluate the influence of the protecting groups of the central diol system on the facial diastereoselectivity. The trimethylsilyl derivative shows the highest selectivity. The bis-cyclobutane containing products have been converted into the enantiopure adducts of gamma-hydroxymethyl-alpha,beta-butenolide and ethylene. (C) 1999 Elsevier Science Ltd. All rights reserved.