Starting from (2R)-bornane-10,2-sultam 1, the useful chiron N-glyoxyloyl-(2R)-bornane-10,2-sultam 5 is prepared via its crystalline precursor 4. The hemiacetal 4 whose structure was proved by the X-ray analysis is formed in diastereomerically pure form. Copyright (C) 1996 Elsevier Science Ltd