title: Synthesis of histidinoalanine: a comparison of β-lactone and sulfamidate electrophiles.
abstract: Previous syntheses of histidinoalanine (HAL) have led to mixtures of regioisomers and/or stereoisomers. For example, opening of N-Cbz-D-serine-β-lactone (6) with Boc-L-His-OMe (5) gave a 2:1 mixture of τ- and π-regioisomers. The sulfamidate 10, derived from N-benzyl-D-serine methyl ester (11), was reacted with Boc-L-His-OMe (5) to give the τ-HAL derivative 17 as a single isomer in 57% yield. A similarly prepared τ-HAL 19, bearing protecting groups that were all hydrogenolytically labile, led to the free bis-amino acid, τ-L-histidinyl-D-alanine (τ-4), as a salt-free standard for amino acid analysis.
authors: Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States. cmtaylor@lsu.edu
authors: Carol M
authors: CM
authors: Taylor
authors: Samanthi Thabrew
authors: ST
authors: De Silva