N-acylimines as intermediates in reactions of α-substituted α-amino acids and dehyroamino acids

✍ Scribed by Richard K. Olsen; Aldean J. Kolar

• Publisher: Elsevier Science
• Year: 1975
• Tongue: French
• Weight: 203 KB
• Volume: 16
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)91373-x

✦ Synopsis

N-Acylimines are of current interest and have been isolated or proposed as intermediates in various reactions 192 ; elimination reactions of a-substituted amides to form N-acylimines have been reported2. During the course of studies on a-substituted a-amino acids, we have observed reactions that are consistent with the formation of N-acylimines as intermediates in both djsplacement reactions on a-substituted II-acylalanines and in addition reactions to dehydroalaninr derivatives. In contrast, limited studies of analogous addition reactions to N-methyldehvdroalanine derivatives indicate that N-acylimmonium ions are not formed as intermediates in these reactions. Treatment of N-acetyl-2-acetylthio-3-chloro-D,L-alanine methyl ester3 (1) [mp 118.5 --120.0' from ether-pet ether (bp 60-900); prepared (51X) by sequentual treatment of N-acetyldehydroalanine methyl ester4 (2) with chlorine and thioacetic acid; nmr (CDC13) 6 2.10 (s, 3H, N-acetyl), 2.30 (8, 3H, S-acetyl), 3.86 (s, 3H, methyl ester), 3.90 and 4.85 (AR doublets, J = 11 Hz, 2H, methylene), 7.27 (m, 18, NH)] with NaOMe in anhydrous methanol at ambient tem-5 perature for 7 minutes Save the 2-methoxyalanine 2 . The formation of 2 can be rationalized as proceeding from 1 by an elimination reaction to give an intermediateN-acylimine 2 with subsequent NHAC N-AC