Phosphonoxins II: diastereoselective synthesis of phosphonic acid analogues of polyoxins.

A diastereoselective synthesis of polyoxin analogues termed phosphonoxin B1 and B2 has been achieved. The key step was sulfinimine-mediated asymmetric formation of ( RS ,2S,3S,4S)-beta-aminophosphonate 3a or (SS ,2R,3S,4S)-beta-aminophosphonate 7 as the major diastereoisomer. A double stereodifferentiation effect was not observed, and the diastereoselectivity is controlled by the absolute configuration of the sulfinyl group.