Synthesis of N-[(3-Amino-1,2-dicarba-closo-dodecaboran-1-yl)acetyl] Derivatives of α-Amino Acids

Abstract

The N- [(3-amino-1,2-dicarba-closo-dodecaboran-1-yl)acetyl] derivatives of α-amino acids were prepared starting from N-protected (Ac, Form, Bz, and Boc) 3-amino-1-(carboxymethyl)-o-carboranes and alkyl esters of natural α-amino acids using the carbodiimide method of coupling and removing the ester groups. All the amides obtained were diastereoisomeric mixtures. Some diastereoisomers were separated and the assignment of the absolute configuration of aminocarborane fragments was performed by X-ray crystallography.

Carbaboranes as Pharmacophores: Properties, Synthesis, and Application Strategies

“…Later on, hydroxyl- para -carbaborane propionic acid was prepared as tyrosine mimetic, and also other carbaboranes furnished with both carboxyl and amino groups at different positions of different cluster isomers. ,, A detailed presentation of the amino acid analogues has already been given by Kabalka and colleagues …”

Synthesis of novel carboranyl derivatives of α-amino acids

“…Earlier, in the synthesis of N [(3 amino 1,2 dicarba closo dodecaboran 1 yl)acetyl] deriv atives of amino acids, we have found that closo carboranes withstand basic hydrolysis under mild conditions. 23 Coupling of carboranylacetic acids 3-5 with com pound 6 at room temperature using N,N´ dicyclohexyl carbodiimide (DCC) in the presence of 1 hydroxybenzot riazole (HOBt) in DMF gave compounds 7-9 in 60-80% yields (see Scheme 1). Compounds 8 and 9 containing the fragments of planar chiral carboranes 4 and 5 were ob tained as mixtures of diastereomers.…”

“…14) and 5 (see Ref. 23) as the starting carborane containing reagents for the preparation of carboranyl derivatives of L lysine (Scheme 1). The starting L lysine derivative used was N α TFA L lysine methyl ester (6), because the N α TFA and COOMe protecting groups can simultaneously be re moved under mild conditions without destruction of the closo carborane cage.…”

“…13,14, 23 Other reagents are commercially available. Melting points were determined on a Boetius instrument; optical rotation was mea sured on a Perkin Elmer M 341 polarimeter.…”

Natural-Product-Directed Catalytic Stereoselective Synthesis of Functionalized Fused Borane Cluster–Oxazoles for the Discovery of Bactericidal Agents

“…The chirality due to such cage substitution has the potential for applications in designing molecules for medicinal chemistry, asymmetric synthesis, and materials science. However, there are limited reports on the enantioselective synthesis of such chiral compounds, and their utility has not been explored. − …”