ISSN:
0170-2041
Keywords:
Asymmetric synthesis
;
Strecker synthesis
;
α-Amino acids
;
Carbohydrate templates
;
Galactosylamine, O-pivaloylated
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The asymmetric synthesis of N-galactosyl D-α-amino nitriles is accomplished by application of 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosylamine (4) as the stereodifferentiating template in Strecker reactions. Aldimines 6 derived from 4 and aromatic or aliphatic aldehydes react with trimethylsilyl cyanide in 2-propanol or tetrahydrofuran in the presence of Lewis acids, e.g. ZnCl2 or SnCl4′ to give the N-galactosyl α-amino nitriles 5 in high yield and with diastereomeric ratios between 6:1 and 13:1 favoring the D diastereomers. Pure D-amino nitrile diastereomers D-5 are obtained in high yields by recrystallization from n-heptane. Acid-catalyzed hydrolysis of compounds D-5 delivers the free D-amino acids. A mechanistic interpretation of the stereoselection observed is given in terms of stereoelectronic, steric and complexing effects exhibited by the carbohydrate.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1991199101117
