Molecular Dynamics-Based Models Explain the Unexpected Diastereoselectivity of the Sharpless Asymmetric Dihydroxylation of Allyl D-Xylosides
✍ Scribed by Nicolas Moitessier; Bernard Maigret; Françoise Chrétien; Yves Chapleur
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 440 KB
- Volume
- 2000
- Category
- Article
- ISSN
- 1434-193X
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✦ Synopsis
The catalytic asymmetric dihydroxylation of several allyl 2-O-benzyl-α-D-xylosides with AD-mix β and PYR(DHQD) 2 shows almost no diastereofacial selectivity if the 3-and 4-OH groups are unprotected or acetylated. Acetal, benzyl ethers and benzoyl esters enhance the diastereoselectivity, in the opposite sense to that predicted by the ''AD mnemonic'', which is completely lost using AD-mix α. In an attempt to understand this behaviour, computational studies of the asymmetric dihydroxylation (AD) of olefins using Sharpless' and Corey's catalysts have been carried out using molecular dynamics. A three-step algorithm was developed taking advantage of the enzyme-like behaviour of catalyst-olefin systems and applied using an ESFF force field. To validate our