Boron Analogues of α-Amino Acids: Synthesis and Characterization of Some Amine-methoxycarbonylboranes and Trimethylamine-(alkylcarbamoyl)boranes

Abstract

Syntheses of a number of amine-methoxycarbonylboranes R2−nHnN·BH2COOCH3 and trimethylamine-(alkylcarbamoyl)boranes, Me3N·BH2CONRR′ are reported. Both types of compounds have been prepared by condensing appropriate amine-carboxyboranes with methanol and an amine, respectively, in presence of dicyclohexylcarbodiimide, and have bean characterized by elemental analysis, IR and NMR (1H and 11B) spectra.

Preparation and Structure Determination of Trimethylamine−Dibromocarboxyborane Esters

“…Several methods have been described for the preparation of amine bromocarboxyborane esters. − Since a boron-attached bromine atom is considered to be a good-leaving group, such compounds are considered as precursors for boron-substituted amine−carboxyboranes, amine·BY 2 X, which are isoelectronic boron analogues of α-amino acids and their derivatives . Amine−carboxyboranes and their derivatives have been shown to possess considerable biological activity. , Alcoholysis of N -ethylnitrilium salts [amine·BH 2 CNEt] + BF 4 - , derived from amine−carboxyboranes under acidic conditions for 48 h, leads to the corresponding esters in 10−34% yield. − Alternatively, alkaline treatment of the N -ethylnitrilium salts and hydrolysis of the intermediate C 5 H 5 N·BH 2 C(OMe)NEt afforded a low yield of C 5 H 5 N·BH 2 CO 2 Me .…”

“…In another procedure, amine−carboxyboranes were reacted with an alcohol in the presence of N , N ‘-dicyclohexylcarbodiimide (DCC) to give the corresponding ester in good yields (50−98%). The drawback of this method is the long reaction time (1−2 weeks), and also, the products were contaminated with dicyclohexylurea. ,− Spielvogel et al synthesized several esters from methyl-, dimethyl-, and trimethylamine complexes of carboxyborane by treatment with alkyl chloroformates, in yields of 31−91% . Esterification of amine−carboxyboranes with alcohols was effective in the presence of a catalytic amount of hydrogen bromide .…”

Synthesis and structure of a 1:1 co-crystal of hexamethylenetetramine carboxyborane and acetaminophen

“…Since we started our endeavor with drug-conjugated carboxyboranes (Ayudhya et al, 2018), we speculated that carboxyboranes may be able to carry more than one drug. In addition to the amine group on the boron atom, ester and amide derivatives at the carboxyborate end have been shown previously (Das et al, 1990).…”

Chemistry of α‐Aminoboronic Acids and their Derivatives

“…This resemblance has inspired extensive biological screening of these molecules, and the promising early results led to the syntheses of a large number of ester [96][97][98][99], amide [100,101], peptide [102,103], hydroxamic acid [104], and transition metal [105][106][107] derivatives of amine-carboxyboranes (A-BH 2 COX, X ¼ OR, NR 1 R 2 , or NHOH) containing a broad range substitutes, among other amine-boranes, which have been reviewed recently [2,108,109].…”