Deaminations of L-valine and L-valine benzyl ester

✍ Scribed by Shun-ichi Yamada; Masao Taniguchi; Kenji Koga

• Publisher: Elsevier Science
• Year: 1969
• Tongue: French
• Weight: 210 KB
• Volume: 10
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)97643-9

✦ Synopsis

There are extensive reports on the deamlnatlone of a-amino aclde and their esters, and the deaminatione of a-amino acids are generally recognized to occur with retention of configuration due to the participation of the neighboring carboxylate group, while the deaminatlons of a-amino acid eetere proceed with racemlzatlon together with an excess invereion about the a-carbon atom. 1) Detailed examination of nitrous acid deamlnation of L-phenylalanlne ethyl ester in acetic acid, however, revealed that varloue rearranged and elimination products were obtained along with the corresponding a-acetoxy eater having 11% net lnveralon of configuration. 8) Since optically active a-amino acids are easily available, it ie of lntereet to examine the stereochemistry of the deamlnatlone of optically active a-amino acid esters. Thle paper deals with an extension of this reaction to the p-substituted allphatic amino acid ester, L-vallne benzyl eater. The deamlnation of L-valine benzyl ester has been briefly reported, but not in detail. 9) To the solution of L-valine benzyl ester ( [a):+ 12.1°(1.740, dloxane)) in acetic acid was addea 1.2 -1.3 molar equivalents of sodium nitrite in portions for about 5 hours at 20 -28°C. After staneing overnight a mixture of neutral reaction products was obtained by working up as usual. GLC analyeia of this reaction mixture gave 12 peaks a8 shown In the Chart ( 4.5 m. 3-5s caxbowax 2OM on Dlaeolid L at a column temperature of 176°C ).

The structures of each peak were identified In the following manner.

Compounds III, IV, VII, VIII, IX and X were Isolated from the reaction mixture and identified with authentic samples by means of IR and NMFi spectra as well ae