The postulated structure of the potent anticancer peptaibol culicinin D has been synthesized using Fmoc-based solid-phase peptide synthesis (SPPS). Comparison of the (1)H NMR data for the reported structure of culicinin D with the data obtained for the two synthetic polypeptides epimeric at C-6 in the AHMOD unit established the C-6 stereochemistry of the AHMOD residue in the natural product to be (R).

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An efficient stereoselective synthesis of fully protected (2S,4R)-4-methylpipecolic acid has been developed. The synthesis was achieved by initial asymmetric α-alkylation of glycine with a chiral iodide, affording the linear precursor as a single stereoisomer. Subsequent aldehyde formation using OsO(4)/NaIO(4) followed by immediate intramolecular cyclization afforded an enamine that was then subjected to hydrogenation to give the final compound in 23% yield over 10 steps.

The synthesis of the antimicrobial cyclic peptide xenematide was accomplished by Fmoc solid phase peptide synthesis and the key esterification reaction was achieved using a modified Yamaguchi esterification. Comparison of the optical rotation and NMR data of the synthesized diastereomers to that of the natural product confirmed the structure of xenematide to be PA-L-[Thr-L-Trp-D-Trp-β-Ala]. (PA = phenylacetyl).