Solid-phase syntheses of Loloatins A-C

The cyclic decapeptides Loloatin A (cyclic L-valyl-L-ornithyl-L-leucyl-D-tyrosyl-L-prolyl-L-phenylalanyl-D-phenylal anyl-L- asparaginyl-L-aspartyl-L-tyrosyl), loloatin B (cyclic L-valyl-Lornithyl-L-leucyl-D-tyrosyl-L-prolyl-L-phenylalanyl-D- phenylalanyl-L-asparaginyl-L-aspartyl-L-trytophanyl) and loloatin C (cyclic L-valyl-L-ornithyl-L-leucyl-D-tyrosyl-L-prolylL-tryptophanyl-D-phenylala nyl-L- asp araginyl-L-aspartyl-L-tryptophanyl) have been synthesized by Fmoc-based solid-phase peptide synthesis, commencing with Asp linked to polystyrene RAM resin through its side chain, and by on resin cyclization of the linear decapeptide through Asp and Asn, followed by cleavage of Asp from the resin. Through the use of a unique combination of DMF/dichloroethane solvent mixture in the coupling steps, and careful monitoring of both coupling and Fmoc deprotection steps, the final cyclic peptides were obtained in overall yields of 31-37\%. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.