An enantiospecific synthesis of (+)-demethoxyerythratidinone from (S)-malic acid: key observations concerning the diastereocontrol in malic acid-derived N-acyliminium ion cyclisations

An unusual syn-selective cyclisation of a TIPS-protected malic acid derived lactam is employed as the key step in an asymmetric synthesis of 3-demethoxyerythratidinone.