First enantioselective synthesis of (-)- and (+)-virgatusin, tetra-substituted tetrahydrofuran lignan.

The first highly enantioselective syntheses of tetra-substituted tetrahydrofuran lignan, (-)- and (+)-virgatusin, were achieved. Hemiacetal was stereoselectively obtained from Evans's syn-aldol product as a single isomer. This hemiacetal was converted to (-)-virgatusin via hydrogenolysis.

Systematic strategy for the synthesis of cyanobacterin and its stereoisomers. 2. Asymmetric total synthesis of the 2- and 3-epimers of dechloro-cyanobacterin.

Stereocontrolled total syntheses of the (2S,3R)- and (2R,3S)-isomers of the non-chlorinated analog of cyanobacterin, a potent photosynthesis inhibitor, were achieved. Since both the (2R,3R)- and (2S,3S)-isomers of this compound had been previously synthesized from the same starting material, a systematic strategy for the synthesis of all stereoisomers could be established.

Systematic strategy for the synthesis of cyanobacterin and its stereoisomers. 1. Asymmetric total synthesis of dechloro-cyanobacterin and its enantiomer.

The stereocontrolled total synthesis of the non-chlorinated analog of cyanobacterin, a potent photosynthesis inhibitor, was achieved by 12 steps in a 10.0% overall yield. Its enantiomer was also synthesized from the same starting material.

Regulated-stereoselective construction of thirteen stereogenic centers necessary for the frame of (+)-discodermolide, based on iterative Lewis acid-promoted aldol reactions.

The segments C(1)-C(13) and C(15)-C(21) containing the 13 stereogenic centers required for the frame of (+)-discodermolide were synthesized in good to excellent enantio- and diastereoselectivities from a common racemic aldehyde, derived from 2-methyl-1,3-propanediol. The enantioselective aldol reactions of the racemic aldehyde with a silylketene acetal, derived from ethyl 2-bromopropionate, in the presence of chiral oxazaborolidinones, prepared in situ with N-p-toluenesulfonyl-(R)- and -(S)-valine and BH(3).THF, proceeded under kinetic control to give the stereotriads with a high degree of enantioselectivity.