T. Yoshinari, F. Gessier, Christian Noti
Nov 1, 2011
Citations
0
Influential Citations
23
Citations
Journal
Helvetica Chimica Acta
Abstract
The preparation of (2S,3S)- and (2R,3S)-2-fluoro and of (3S)-2,2-difluoro-3-amino carboxylic acid derivatives, 1–3, from alanine, valine, leucine, threonine, and β3h-alanine (Schemes 1 and 2, Table) is described. The stereochemical course of (diethylamino)sulfur trifluoride (DAST) reactions with N,N-dibenzyl-2-amino-3-hydroxy and 3-amino-2-hydroxy carboxylic acid esters is discussed (Fig. 1). The fluoro-β-amino acid residues have been incorporated into pyrimidinones (11–13; Fig. 2) and into cyclic β-tri- and β-tetrapeptides 17–19 and 21–23 (Scheme 3) with rigid skeletons, so that reliable structural data (bond lengths, bond angles, and Karplus parameters) can be obtained. β-Hexapeptides Boc[(2S)-β3hXaa(αF)]6OBn and Boc[β3hXaa(α,αF2)]6-OBn, 24–26, with the side chains of Ala, Val, and Leu, have been synthesized (Scheme 4), and their CD spectra (Fig. 3) are discussed. Most compounds and many intermediates are fully characterized by IR- and 1H-, 13C- and 19F-NMR spectroscopy, by MS spectrometry, and by elemental analyses, [α]D and melting-point values.