[reaction: see text] The preparation of depsi-peptides, amide-to-ester-substituted peptides used to probe the role of hydrogen bonding in protein folding energetics, is accomplished by replacing specific l-alpha-amino acid residues by their alpha-hydroxy acid counterparts in a solid-phase synthesis employing a t-Boc strategy. Herein we describe the efficient stereoselective synthesis of all 19 appropriately protected alpha-hydroxy acid equivalents of the l-alpha-amino acids, employing commercially available materials, expanding the number of available alpha-hydroxy acids from 9 to 19.
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