D,L-Glutamic acid (I) was sequentially protected as the gamma-allyl ester (III), upon treatment with allyl alcohol (II) and chlorotrimethylsilane, followed by conversion to the trichloroethyl carbamate (V) by means of chloroformate (IV), and then reaction of (V) with benzyl bromide to afford the alpha-benzyl ester (VI). Deprotection of the trichloroethyl carbamate of (VI) by treatment with zinc dust and HOAc and subsequent condensation of the resulting amine with decanoyl chloride (VII) furnished amide (VIII). The allyl ester of (VIII) was then selectively cleaved by using tetrakistriphenylphosphine palladium(0) and morpholine to give carboxylic acid (IX). trans-1,2-Diaminocyclohexane (X) was protected as the mono tert-butyl carbamate (XI) and then coupled with acid (IX) in the presence of diethylphosphoryl cyanide to yield amide (XII). After acidic Boc cleavage of (XII), coupling of the resulting amine with 2,5-diphenyloxazole-4-carboxylic acid (XIII) by means of bromo-tris(pyrrolidino)phosphonium hexafluorophosphate (PyBroP) afforded (XIV). Finally, hydrolysis of the benzyl ester of (XIV) with LiOH provided the corresponding carboxylic acid.

D,L-Glutamic acid (I) was sequentially protected as the gamma-allyl ester (III), upon treatment with allyl alcohol (II) and chlorotrimethylsilane, followed by conversion to the trichloroethyl carbamate (V) by means of chloroformate (IV), and then reaction of (V) with benzyl bromide to afford the alpha-benzyl ester (VI). Deprotection of the trichloroethyl carbamate of (VI) by treatment with zinc dust and HOAc and subsequent condensation of the resulting amine with decanoyl chloride (VII) furnished amide (VIII). The allyl ester of (VIII) was then selectively cleaved by using tetrakistriphenylphosphine palladium(0) and morpholine to give carboxylic acid (IX). trans-1,4-Diaminocyclohexane (X) was protected as the mono tert-butyl carbamate (XI) and then coupled with acid (IX) in the presence of diethylphosphoryl cyanide to yield amide (XII). After acidic Boc cleavage of (XII), coupling of the resulting amine with 2,5-diphenyloxazole-4-carboxylic acid (XIII) by means of bromo-tris(pyrrolidino)phosphonium hexafluorophosphate (PyBroP) afforded (XIV). Finally, hydrolysis of the benzyl ester of (XIV) with LiOH provided the corresponding carboxylic acid.