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Chiral enolate derived from (4R)-4-tert-butyldiphenylsilyloxymethyl-4-butanolide 10 with lithium hexamethyldisilyazide (LiHMDS) was treated with trisyl azide, followed by addition of TMSCl to give (2S,4R)-2-azido-4-[(tert-butyldiphenylsilyloxy)methyl]-4-butanolide 8 (53%), from which the first total synthesis of polyoxin M (1) was achieved in overall 3.2% yield (13 steps) from d -glutamic acid. Moreover, the synthesis of the reported synthetic intermediate (2S,4R)-4-hydroxyornithine congener 6 for biphenomycins A and B was also achieved in overall 4.1% yield (12 steps) from d -glutamic acid. |
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