Enantiodivergency and enantioconvergency in the synthesis of the dendrobate alkaloid 241D.

A diastereodivergent preparation of two N-alkenylnitrones (9 and 11) from easily available (R)-2,3-O-cyclohexylideneglyceraldehyde (5) led to an enantiodivergent synthesis of both enantiomers of the dendrobate alkaloid 241D in a sequential two-directional approach involving intramolecular nitrone cycloaddition as the key step. Either of these two nitrones could, in principle, be utilized for the preparation of the title compounds in an enantioconvergent fashion as well. The methodology was extended to prepare an analogue (33) of (-)-241D.