Hydroxylated Derivatives, Streptovitacins A and C2, and E-73

Streptovitacins A (STV-A, 18) [9], B (19), and C2 (20) [9,19] isolated from Streptomyces griseus, and E-73 (13-acetoxycycloheximide, 21) [20] from S. al-bulus are oxygenated derivatives of 1 (Fig. 3). Oritani et al. synthesized 18, 20, and 21 to investigate the effect of oxygen functionalities on antimicrobial activities [21,22].

As shown in Scheme 3, they prepared two possible stereoisomers of 20 [21]. Introduction of a methyl group by Grignard reaction to (+)-(R)-pulegon (22) gave 23, which was subjected to ozonolysis to afford 24. The tertiary hydroxyl group was protected as TMS ether (25) and subsequent aldol reaction with aldehyde 7 provided (-)-(2R,4R,6R,aS)-STV-C2 (20a) as a single diastereomer. On the other hand, racemic ketone (±)-11 was hydroxylated via

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