Asymmetric reduction of aryl trifluoromethyl ketones with an achiral NADH model compound in a chiral hydrophobic binding site of sodiumcholate micelle, β-cyclodextrin and bovine serum albumin
✍ Scribed by Naomichi Baba; Yasuo Matsumura; Toyonari Sugimoto
- Publisher
- Elsevier Science
- Year
- 1978
- Tongue
- French
- Weight
- 204 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Recent interest in asymmetric reduction has emphasized the exploration of model reactions for stereospecific dehydrogenase-catalysed reduction of carbonyl compounds in the presence of NADH. While the asymmetric reductions bearing on the NADH model have been done by introducing chiral centre(s) exclusively into the 1,4-dihydronicotinamide moiety and/or substrate,' there is to date no research with achiral NADH model analogues in a chiral environment. Asymmetric induction of this type has been the subject of much interest in surveying a newer method of asymmetric transformation. The present communication describes an asymmetric reduction of aryl trifluoromethyl ketones ((2) -o;C)) with a watersoluble l-propyl-1,4-dihydronicotinamide (NAH) as an achiral NADH model compound in the aqueous solution of sodium cholate (NaC) micelle, 2 6-cyclodextrin (B-CD) and bovine serum albumin (BSA), each of which has a chiral hydrophobic binding site capable of including water insoluble guest ketones. In addition, results on NaBH4 reduction in the same condition were compared with those by NAH. To a 0.01 M borate buffer solution (pH 9.2) of g -s (5.0 mM) in the presence of NaC (0.4 M), B-CD (0.05 M) or BSA (1.5 -1.7 mM)3 was added NAH (0.025 M) or NaBH4 (0.01 M) and th e mixture was stirred at 25°C in the dark for a week.
The product alcohol was extracted with ether or trichloroethylene, followed by preparative vpc to give the pure material. The chemical yields in the NAH and NaBH4 reductions were 20 -60% and quantitative respectively by vpc analysis.
From optical rotation of the alcohol the enantiomeric excess was calculated.