Unexpected Formation of Optically Active 4-Substituted 5-Hydroxy-γ-[nl]lactams by Organocatalyzed Reaction of 3-Substituted Cyclobutanones with Nitrosobenzene.

An organocatalyzed enantioselective desymmetrization reaction for converting 3-substituted cyclobutanones into 4-substituted 5-hydroxy-γ-lactams is presented. This involves a ring-expanding <italic>O</italic>-nitroso aldol-cyclization domino sequence. This synthetic protocol provides access to five-membered ring systems in good yields with the generation of two new stereogenic centers. [ABSTRACT FROM AUTHOR]