Diastereoselective synthesis of 3-hydroxy-3-phenyl-cyclobutanoic derivatives by photocyclization

Irradiation of 2-substituted 4-oxo-4-phenyl-butanoic amide 1a and esters 1b -f affords the corresponding cyclobutanols 4, 5 and 6. The diastereoselecti vity of photocyclization depends on carboxyl and gamma-substituents. In the case of pyrrolidide 10 products 13 and 14 which are formed via a competiti ve epsilon-hydrogen transfer are obtained along with 2, 11 and 12 which are the result of gamma-hydrogen abstraction. The relative configurations of t he photoproducts 4-6 and 12-14 are established by NMR and X-ray analysis. ( C) 1998 Elsevier Science S.A. All rights reserved.