1-Oxacephem Antibiotics

1-Oxacephem antibiotics, in which the 1-sulfur atom in cephalosporins is replaced by oxygen, show marked enhancement in their antibacterial activity. This finding led to intensive efforts toward establishing a stereocontrolled and industrially feasible method for their production. One method along a synthetic route involving epi-oxazoline (46), allylic alcohol (47), its cyclized 3-methylene-1- oxacepham (48) and 7α-methoxy-7β-amino-1-oxacephem (41) was found to be the most efficient for producing 1-oxacephamycin-type antibiotics, such as latamoxef (11a), flomoxef (11b), and 2355-S (11c).