Synthesis of L‐ and D‐4,6‐Dideoxyhexoses and 4,6‐Dideoxy‐C‐phenylglycosides from Enzyme‐Generated Products

Abstract

Optically active 1,3‐diols 1 were prepared by biocatalysed routes. The synthetic versatility of compounds 1 as chiral building blocks was shown. The oxidative cleavage of the double bond afforded a carbonyl moiety, which allowed for elongation by Grignard addition and further derivatisation to make deoxy sugars readily available. The epoxidation of the same double bond allowed the direct intramolecular opening of the epoxide ring to generate deoxy C‐phenylglycosides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Baker's Yeast Reduction of β‐Hydroxy Ketones

“…We have recently been involved in investigations of baker's yeast reductions9 of syn ‐ and anti ‐ 1 (Scheme ), which afforded a 1:1 mixture of the enantiomerically pure diols (1 S ,2 S , R )‐ anti , anti ‐ 2 and (1 S ,2 R , S )‐ anti , syn ‐ 2 . This was quite a novel finding because β‐hydroxy ketones are typically the final products of baker's yeast reductions of β‐diketones,5g,10 and in most cases they are not further transformed.…”

Klebsiellapneumoniae (NBRC 3319) Mediated Asymmetric Reduction of α‐Substituted β‐Oxo Esters and Its Application to the Enantioiselective Synthesis of Small‐Ring Carbocycle Derivatives

“…The enantiopure triols 24 and 25 can serve as potential precursors for 5Ј-methylaristeromycin and related analogues. [16] The structure of 21 was confirmed unambiguously by single-crystal X-ray analysis of the corresponding bis(para-nitrobenzoate) derivative. The ORTEP representation of this structure can be found in the Supporting Information.…”

Recent advances in the stereoselective synthesis of 1,3-diols using biocatalysts

“…A versatile method of preparing enantiomerically pure 1,3-diols is by the stereoselective bio/chemocatalytic reduction of b-hydroxy ketones, which are obtained either from the corresponding dicarbonyl compounds 27,28 or via an aldol reaction. 29 Brenna et al described the stereoselective synthesis of 1,3diols from the corresponding hydroxy ketones by the baker's yeast reduction, 30 which was quite a novel finding because b-hydroxy ketones are typically the final products of the baker's yeast reduction of diketones 31 and in most cases they are not further transformed. This extraordinary selectivity of the baker's yeast reduction prompted the same group to develop methods for simultaneous control over the configurations of multiple stereogenic centres.…”

“…Later, as an extension to the study, the authors demonstrated the synthesis of the single stereoisomer of the 1,3-diol 85 with defined stereochemistry at three adjacent stereogenic centres and this was used as a chiral synthon to prepare biologically active molecules such as 4,6-dideoxyhexoses 88 and 4,6-dideoxy-C-phenylglycosides 89, which contain nonoxygenated carbon atoms at positions 4 and 6 in the sugar ring. 30 The synthetic procedure as depicted in Scheme 20 involves the aldol condensation of cyclopentanone and cinnamaldehyde giving a mixture of two diastereomeric hydroxy ketones synand anti-86, which were submitted to a NaBH 4 reduction to afford the four racemic diastereomeric diols 85. The syn,syn-85 diol was isolated from this reduction mixture by column chromatography and was submitted to a lipase PS mediated transesterification in tert-butyl methyl ether in the presence of vinyl acetate as the acyl donor.…”