J. Van der Eycken

Iridoids: enantioselective synthesis of loganin via an asymmetric Diels-Alder reaction

Abstract Starting from (-)-camphor-10-sulfonic acid ( 5 ) the crystalline sultam 9 was readily prepared. TiCl4-mediated Diels-Alder addition of the N-crotonoyl sultam 11 to cyclopentadiene, crys- tallization of the resulting adduct 12 and subsequent reduction gave virtually pure (1S, 4R, 5R, 6S)- 1 together with recovered auxiliary 9 . The loganin precursor 1 was transformed into norbornanone 20 , which upon Baeyer-Villiger oxidation led to the suitably substituted cyclo- pentane 22 from which 1-B-O-methyl loganin aglucone ( 2 ) was rea- dily available.

Enantioselective total synthesis of (−)-epipodophyllotoxin and (−)-podophyllotoxin

Abstract An enantioselective total synthesis of (−)-epipodophyllotoxin (2) and hence of (−)-podophyllotoxin (1) is described, involving as key steps a conjugate addition on butenolide 13 as the chiral template, a stereoselective aldol condensation on 11a and a stereoselective ring closure of 8.

The synthesis of 2-azapodophyllotoxins

Abstract 2-Azapodophyllotoxins, tetrahydroisoquinoline analogues of podophyllotoxin have been synthesized. They constitute a new class of highly potent anti-tumor agents.

The synthesis of 4-desoxy-2-azapodophyllotoxins

Abstract 4-Desoxy-2-azapodophyllotoxins, tetrahydroisoquinoline analogues of podophyllotoxin, have been synthesized and evaluated for their anti-tumor activities.

The synthesis of optically active derivatives of erythritol

Abstract The acetonides 2 and 4, obtained from erythritol, are excellent substrates for SAM II lipase. The resulting homochiral mono-esters 3 and 5 are suitable chiral building blocks.

Enzymatic enantioselective hydrolysis of 2,2-dimethyl-1,3-dioxolane-4-carboxylic esters

Abstract 2,2-Dimethyl-1,3-dioxolane-4-carboxylic acid derived chiral building blocks were prepared from substituted α,β-unsaturated acids with high enantiomeric purities by enzymatic hydrolysis of their n.butyl esters.

Enantiotoposelective PLE-catalyzed hydrolysis of cis-5-substituted-1,3-diacyloxycyclohexanes. Preparation of some useful chiral building blocks

Abstract PLE-catalyzed hydrolysis of prochiral cis-5-benzyloxymethyl-1,3-diacetoxycyclohexane and cis-5-benzyloxy-1,3-diacetoxycyclohexane proceeds with high enantiotoposelectivity. The preparation of some useful chiral building blocks is described.

Total synthesis of (±)-podophyllotoxin and (±)-epipodophyllotoxin

Abstract A novel approach to ( + )-epipodophyllotoxin ( 2c ) and hence also to ( + )-podophyllotoxin ( 1c ) is described, involving as a key-step the stereoselective ring closure of the TMS-ester derived from 17a to the tetralin derivative 30c with mesyl chloride.

Iridoids : The structure elucidation of specionin based on chemical evidence and 1H NMR analysis

Abstract The iridoid specionin is an effective antifeedant against the Eastern spruce budworm. Previous synthetic work has shown that the proposed structure was incorrect. Presently the total synthesis of the revised structure 2C is described. The structure elucidation, with special emphasis on the anomeric C-3 configuration, is based on chemical evidence and 1H NMR analysis.

The synthesis of chiral isopropylidene derivatives of 1,2,3-cyclohexanetriols by enzymatic differentiation

Abstract 2,3-O-Isopropylidene-1-cyclohexanol chiral building blocks have been prepared with high enantiomeric purities by enzymatic hydrolysis of their racemic acetates or n.butyrates.