Preparation and Properties of N-Monoalkylated Imidic Esters.

A Synthesis of Acetamidines

“…Although the separation/purification of this particular amidine is fairly easy, 6b increased formation of the imidate ester means a reduction in the yield of the desired amidine. The δ values of the signals in 1 H and 13 C NMR spectra of methyl N-octylacetimidate 6b perfectly matched the new signals of the impurity in the sample obtained from the reaction of higher amines such as tetradecyl and hexadecyl amine by method 1. The chemical shifts of the R -CH 2 -of the imidate ester derived from the simple aliphatic amines (Table 2, entries 1-7) are downfield (by approximately 0.2 δ) compared to the peaks obtained for the imidate ester from the amine with the PEG chain because of the ethereal O-atom on the β-carbon atom.…”

“…The 1 H and 13 C{ 1 H} NMR spectra of 6b prepared by the literature method match those of the impurity obtained from the reaction of 3g with 5.…”

“…Similar impurities were observed in other acetamidines prepared by this method. An NMR study including 1 H, 13 C{ 1 H}, DEPT-135, and HSQC NMR spectroscopy showed that the impurity contains two new methyl groups at δ C 14.50/δ H 1.58 and δ C 52.06/δ H 3.55, a new CH 2 group at δ C 49.69/δ H 3.28 and at least three CH 2 peaks at 70.05, 70.96, and 72.41 that are visible beside the peaks of 4g in the 13 C NMR spectrum. 12 All of those CH 2 peaks of the impurity are very closely matched to the CH 2 peaks for 4g, suggesting that the impurity had the same tail group as the desired amidine 4g but a different headgroup.…”

N-Ethylamino acid synthesis and N-acylamino acid cleavage using Meerwein's reagent

“…The results are in general agreement with those of Pilotti et al (14) who succeeded with the deacetylation but failed with the debenzoylatioil of acylamines, and Hanessian (13) who cleaved acetamino sugars by this method. They are also in agreement with the synthetic work of Borch (10).…”

Multiple alkylation and mapping of the active site of .alpha.-chymotrypsin by carbonium ions generated with active-site-directed enzyme-activated nitrosoamide substrates

“…O-Benzyl-Ser and -Thr, '-benzyl-His, -Phe, -Pro, -Thr, -Tyr, and -Val, and S-benzylhomocysteine were obtained from Vega-Fox Biochemical Co., O-benzyltyrosine, 5-benzylcysteine, and /V3lm-benzylhistidine were obtained from Aldrich Chemical Co., and TV-benzylisoleucine was obtained from Accurate Chemical and Scientific Co. /V-Benzyl-Ala, -Glu, -Leu, -Lys, and -Ser were prepared as described by Quitt et al 27 and A-benzyl-Cys and -Met as described by Kanao and Sakayori.28 TV-Benzyl-Asp was prepared as described by Frankel et al 29 and TV-benzyl-Gly as described by Baker et al30 S-(Benzylthio)cysteine was prepared by the method of Nogami et al, 31 and the S-benzylsulfonium salt of methionine was prepared by the method of van Bergen et al32 Finally, 3-benzyltyrosine was prepared by the method of Iselin.33 Benzyl JV-Ethylacetimidate. This compound was prepared by the methods of Pilotti et al 34 and Bredereck et al 35 The stable form is believed to be the Z isomer. 36 The syntheses of the 13C-enriched inhibitors 1 and 2 followed the procedures of White et al4 except in the synthesis of methyl alaninate hydrochloride.…”