Aliphatic Derivative, Streptimidone

Among a group of aliphatic derivatives 39-42 [33-36], streptimidone (39), isolated from various Streptomyces species [37,38] and Micromonospora coerulea [39], showed strong antimicrobial activity against eukaryotic cells [38]. Oritani et al. synthesized all four diastereomers of streptimidone to investigate its antimicrobial activity (Scheme 6) [40]. Alcohol (S)-43 [41] derived from methyl (S)-3-hydroxy-2-methylpropanoate (99.9% ee) was converted to aldehyde 44, and this was coupled with phosphine oxide reagent 45 [42] to afford diene 46. The TBS protecting group was removed, and the resulting hydroxyl group was oxidized to give ketone 47. Finally, an aldol reaction of 47 with 7 [43], gave the unnatural enantiomer of streptimidone, (±)-(2;S,5'R)-39, and its 2'-epimer. The overall yields were 6.8%

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