Functionalized platforms based on marine cyclopeptides: different pathwaysto the hexapeptide

The synthesis of macrocyclic, roughly planar, exclusively syn-functionalize d hexapeptides, related to dolastatin I and bistratamide C from enantiomeri cally pure oxazole precursors is reported. The platforms can either be synt hesized in a stepwise procedure by final cyclization of the linear oxazole trimers or in a direct 'one-pot' reaction. The investigation on the couplin g of these building blocks into linear dimers and trimers with modern pepti de coupling reagents is reported. (C) 2000 Published by Elsevier Science Lt d.