The enantioselectivesynthesis of chiral N,N‐acetals derived from α‐dicarbonyl compounds has been achieved. Good yields and enantioselectivities were observed for the reaction with various α‐dicarbonyl compounds with 2‐aminobenzamides using chiral bis(imidazoline)‐phosphoric acid catalysts. Based on these experimental investigations, a possible transition state is proposed to explain the origin of
Cephalosporin compounds of the formula:
wherein R1 is amino or protected amino; R2 is substituted or unsubstituted heterocyclic group having 1 - 3 hetero atoms selected from oxygen and sulphur; R3 is carboxyl or protected carboxyl; R4 is nucleophilic compound residue; R5 is carboxyl, protected carboxyl and -COO-, a pharmaceutically acceptable salt thereof and their synthetic intermediate of the formula:wherein R11 is amino or protected amino; R2 is substituted or unsubstituted heterocyclic group having 1 - 3 hetero atoms selected from oxygen and sulfur; R3 is carboxyl or protected carboxyl; -COOY is carboxyl or protected carboxyl. Said cephalosporin compound is useful as antibacterial agent.