A convergent synthesis of all S-configurated diastereoisomer of RP-66453 (aS,S,S,S,S,S), a peptide secondary metabolite, has been developed. The synthesis is notable for its brevity, partly because functionalized amino acids can be used directly. By combination of chem. evidence and NMR data, the abs. configuration of RP-66453 was detd. to be (aR,S,S,S,S,S). It is interesting to note that nature created RP-66453 with a thermodynamically less stable atropisomer, while lab. synthesis using intramol. Suzuki-Miyarura coupling as the last ring-closure step produced the thermodynamically more stable isomer. [on SciFinder (R)]