Synthesis of [S-[1-C-14]Val(7)]VALSPODAR application of (+)/(-)-[C-13,14(n)]BABS and (+)/(-)-[C-13,14(n)]DPMGBS, part 4

VALSPODAR (2) under bar, a cyclic undecapeptide anticancer drug derived fro m natural Cyclosporin D <(10)under bar>, was labelled with carbon-14 in a n ine step synthesis. The sequence started from (-)-[1-C-14]BABS <(1a)under b ar>, a highly versatile two-carbon synthon for a broad spectrum of singly/m ultiply labelled substance classes, which after conversion to (-)-[1-C-14]D PMGBS <(1b)under bar> and subsequent alkylation with isopropyl iodide gave e.p. N-Boc-S-[1-C-14]valine (7) under bar in 46% yield. Coupling to the res pective linear decapeptide P-D(8->6), followed by cyclization and selective oxidation afforded the labelled drug substance in an overall radiochemical yield of 9%.