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Strategies for the Formation of 1-Dethia-1-oxa-cephams

✍ Scribed by Z Kałuża; B Furman; P Krajewski; M Chmielewski

Book ID
104202772
Publisher
Elsevier Science
Year
2000
Tongue
French
Weight
187 KB
Volume
56
Category
Article
ISSN
0040-4020

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✦ Synopsis

AbstractÐThe paper describes three possible routes for the formation of 1-dethia-1-oxa-cephams. The ®rst two routes: (a) [212]cycloaddition to chiral vinyl ethers and (b) condensation of 4-acetoxyazetidin-2-one to chiral alcohols, are followed by the ring closure step involving N-alkylation. The third route (c) consists of N-alkylation prior to the cyclization step. In order to compare routes (a), (b) and (c), diastereomeric 1-dethia-3-(4-methoxybenzyloxy)-1-oxacephams were synthesized using three possible strategies. While the comparison of stereoselectivities of the [212]cycloaddition method (a) and the condensation (b) shows unequivocally the advantage of the former, the route (c) leads to the reverse direction of asymmetric induction relative to the ®rst two steps and offers the highest asymmetric induction.

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