Dipeptide, synthetic strategy

The authors applied the same synthetic strategy to racemic 4-alkyl -(iodo-methyl)-2-phenyl-5(4/ )-oxazolones 266 and obtained a diastereomeric mixture of oxazolines 267 and 268 (Scheme 7.86). The diastereoisomers were separated chromatographicaUy and then converted into dipeptides incorporating an a-alkyl-serine residue. ... 

A synthetic strategy based on the attachment to the resin of Lys/Om side chains, as reported before and on Kates on-resin cyclization method was exploited by Andreu et al. [33] for the preparation of the antibiotic gramicidin S, cyc/o(Val-Om-Leu-DPhe-Pro)2, the corresponding Lys analogue, and a further derivative containing a dipeptide surrogate of type II /3-turns, the 2-amino-3-oxohexahydroindolizino[8,7-/ ]indole-5-carboxylate system (IBTM). 

The dipeptide ester L-Asp-L-Phe-OMe (Aspartame) is used in large amounts as a low-calorie sweetener. One of the most economical strategies for its synthesis involves an enzymatic step, which is run at a capacity of 2,000 t ear (Scheme 3.25). Benzyloxycarb(Miyl-(Z)-protected L-aspartic acid is linked with L-Phe-OMe in a thermodynamically cOTitroUed cmidensation reaction catalyzed by the protease thermolysin without formation of the undesired (bitter) (3-isomer. Removal of the product via formation of an insoluble salt was used as driving force to shift the equilibrium of the reaction in the synthetic direction [318, 319]. 

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