A Conventional New Procedure for N-Acylation of Unprotected Amino Acids

Abstract

The preparation of amide derivatives (4) by N-acylation of unprotected a a-amino acids is easily achieved via readily available benzotriazolyl carboxylates (2a-d) or succinimidyl carboxylates (2e-f). These intermediates (2) are prepared from reaction of carboxylic acids (1) with 1-hydroxybenzotriazole (HO-Bt) or N-hydroxysuccinimide (HO-Su) in the presence of equimolar amounts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (WSCI). The overall yields of the target compounds (4) were excellent, and this two-stage procedure could be applicable as an alternative procedure for one-pot reaction.

Preferential Intramolecular Ring Closure of Aminoalcohols with Diethyl Carbonate to Oxazolidinones

“…Since the experiment using compound 1 under similar reaction conditions reported previously 2) resulted in a quite complex reaction mixture by TLC analysis, it is not used to determine conditions suitable for cyclization of this aminoalcohol (1). Then, we tried the cyclization of (1) under the conditions of this aminoalcohol (1) and (EtO) 2 CO in a 1/1.25 ratio.…”

“…The preparation of racemic b-aminoalanines as starting materials has already been described in our previous paper. [1][2][3][4] The following abbreviations in the brackets were used for the cyclohexane ring (Cyhx), the piperidine ring (Ppd), and for the oxazolidinone ring (Oxaz), respectively.…”

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In connection with our interest in the chemistry of baminoalanines, [1][2][3][4] we have reported the synthetic application of these materials as a synthon for the preparation of a 5-membered oxazolidinone ring system.2) Some of the oxazolidinone derivatives have attracted much attention not only as a synthetic target but also because of the importance of the related compounds in the biological activities. 5,6) This paper deals with the relative rates of ring closure by cyclization with diethyl carbonate (EtO) 2 CO from aminoalcohols as starting material.

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“…In connection with our interest in the chemistry of baminoalanines, [1][2][3][4] we have reported the synthetic application of these materials as a synthon for the preparation of a 5-membered oxazolidinone ring system.…”

Total synthesis of lamellarin G trimethyl ether through enaminone cyclocondensation

“…According to a modified procedure. 38 To a solution of 2-bromo-4,5-dimethoxybenzoic acid ( 5 ) (500 mg, 1.91 mmol) in dry DCM (10 mL), HOBt hydrate (380 mg, 2.48 mmol, 1.3 equiv.) and EDC hydrochloride (475 mg, 2.48 mmol, 1.3 equiv.)…”