Chiral enolate derived from (4R)-4-tert-butyldiphenyisilyloxymethyl-4-butanolide 10 with lithium hexamethyldisilyazide (LiHMDS) was treated with trisyl azide, followed by addition of TMSCI to give (2S,4R)-2-azido-4-[(tei-t-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-hydroxyomithine congener 6 for biphenomycins A and B was also achieved in overall 4.1% yield (12 steps) from D-glutamic acid. (c) 2006 Elsevier Ltd. All rights reserved.
Improved synthetic methods for the preparation of three differently protected (2S,4R)-4-hydroxyornithines (10, 16, 24) have been developed which obviously can be used for the construction of the other stereoisomers. Formation of the corresponding α, β-didehydroamino acid derivatives (4, 15, 22) and their enantioselective hydrogenation are the characteristic steps of these syntheses.
Chiral enolate derived from (4R)-4-tert-butyldiphenyisilyloxymethyl-4-butanolide 10 with lithium hexamethyldisilyazide (LiHMDS) was treated with trisyl azide, followed by addition of TMSCI to give (2S,4R)-2-azido-4-[(tei-t-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-hydroxyomithine congener 6 for biphenomycins A and B was also achieved in overall 4.1% yield (12 steps) from D-glutamic acid. (c) 2006 Elsevier Ltd. All rights reserved.