Abstract
Akabori reported that the reaction of N-methylalanine (1) with benzaldehyde at 130 oC for 1 h in pyridine gave pseuido-ephedrine in 16% yield (Nipponkagakukaishi 1942, 64, 608-611). We have already reported on this symposium (last year) that the reaction of 1,3-benzodioxole-5-carbaldehyde (piperonal) with 1 gave the amino alcohol derivative in good yield (87% yield as a mixture of diastereomer) via unstable 3,4-dimethyl-2,5-diphenyl-oxazolidine as an intermediate. We further investigated the reaction condition of this reaction in detail. As a result, we could improve the reaction as follows: 1) The molar ratio of 1 could be decreased to 2 mol eq. from 6.5 mole eq. 2) DMSO or cyclopentyl methyl ether (CPME) could be used as a solvent. 3) The reaction temperature could be decreased to 85 oC from 130 oC.
The present results are very useful information in order to develop the diastereo- and stereo-selective reactions.
