By condensation of cyclopeptide (I) with 4''-(pentyloxy)-p-terphenyl-4-carboxylic acid 2,4,5-trichlorophenyl ester (II) by means of dicyclohexylcarbodiimide (DCC) in DMF at room temperature.
A new synthesis of LY-303366 has been reported: The enzymatic hydrolysis of echinocandin B (I) with Actinoplanes utahensis provides the corresponding cyclic peptide (II), which is then reacylated with the active ester 4''-(pentyloxy)-p-terphenyl-4-carboxylic acid 2,4,5-trichlorophenyl ester (III) in DMF. The active ester (III) is obtained as follows: 4-Bromo-4'-(pentyloxy)biphenyl (IV) is treated with sec-butyllithium and triisopropyl borate in THF/cyclohexane, yielding (after hydrolysis with HCl) 4'-(pentyloxy)biphenyl-4-boronic acid (V), which is condensed with methyl 4-iodobenzoate (VI) by means of palladium tetrakis(triphenylphosphine) and K2CO3 in refluxing toluene, giving 4''-(pentyloxy)-p-terphenyl-4-carboxylic acid methyl ester (VII). The hydrolysis of (VII) with NaOH in refluxing dioxane containing 2N NaOH affords the corresponding free acid (VIII), which is finally converted to the active ester (III) by esterification with 2,4,5-trichlorophenol (IX) by means of dicyclohexylcarbodiimide (DCC) in DMF.