Synthesis of l-2,3-trans-3,4-cis-dihydroxyproline building blocks for peptide synthesis

L-2,3-trans-3,4-cis-N-Fluorenylmethoxycarbonyl-3,4-dihydroxy-3,4-O-isopropylidineproline (9) has been prepared from D-gulonolactone in nine steps and an overall yield of 22%. Compound 9 has been converted to its allyl ester 13. Compounds 9 and 13 were investigated as building blocks for the incorporation of dihydroxyproline into peptides, with compound 9 serving as a carboxyl component and compound 13 as a precursor to an amino component for peptide coupling reactions. Their utility was demonstrated by the synthesis of dipeptides 11 and 15.