103745-07-9

We have succeeded in the easy preparation of optically active 1,2-diol monotosylates bearing an unsaturated substituent via enzymatic hydrolysis. Lipase PS quickly catalyzes the hydrolyses of 2-acetoxybut-3-enyl tosylate, which has a double bond, and 2-acetoxybut-3-ynyl tosylate, which has a triple bond, with excellent enantioselectivity to afford the corresponding optically active compounds. The reaction is also applicable to acetates with a longer chain, which has a double bond at the terminus. To demonstrate the applicability of this method, enantiomerically pure (R)-massoialactone, a natural coconut flavor, has been synthesized from racemic 2-acetoxypent-4-enyl tosylate in several steps. Furthermore, the enzyme can recognize the stereochemistry of olefins, and the (Z)-alkenyl structure is more suitable for the enantioselective hydrolysis than the (E)-isomer.

The C-1 reactivity of 2,3-epoxy alcohols and derivatives has been examined thoroughly.In the first approach a rearrangement opening of 2,3-epoxy alcohols with LiI leads to 1-iodo 2,3-diols with erythro or threo stereochemistry starting from trans or cis epoxy alcohols.Subsequent coupling with a carbon nucleophile can lead to a series of vicinal diols with predicted relative and absolute stereochemistry: the described methodology has been applied to the asymmetric synthesis of the naturally occuring (S,S)-2,3-octanediol and (R,R)-muricatacin.The second approach, starting from easily available tosyloxy epoxides, leads to the highly regioselective opening of the oxirane ring with Li halides.The 3-iodohydrins obtained can be reduced to the corresponding 1-(tosyloxy)alkan-2-ols and then coupled with common carbon nucleophiles to afford, in high yields, optically active alcohols.This methodology has been applied to the asymmetric synthesis of naturally occuring pheromones like 3(R)-octanol and 4(R)-dodecanolide.

2,3-epoxy alcohols-1-tosylates are regio and chemoselectively opened to the corresponding 3-halohydrins (I, Br, Cl): the reduction of the iodohydrins to the monoprotected diols and subsequent standard coupling of the tosyl group leads to a straightforward synthesis of optically active naturally occurring pheromones

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