Acylation of the tertiary 20-hydroxy group of camptothecin (I) with N-Boc-valine-N-carboxyanhydride (II) afforded the corresponding ester (III). Subsequent acidic N-Boc group cleavage gave amino ester (IV). This was coupled with N-Boc-histidine (V) to furnish, after treatment with trifluoroacetic acid, the histidyl-valyl camptothecin ester (VI).

Regioselective O-methylation of p-nitrophenyl-beta-L-fucopyranoside (VII) by means of dibutyltin oxide and iodomethane provided the 3-O-methyl pyranoside (VIII). Subsequent catalytic hydrogenation of the nitro group of (VIII) over PtO2 gave aniline (IX), which was further converted to the isothiocyanate (X) upon treatment with thiophosgene and ethyl diisopropylamine. Finally, coupling between isothiocyanate (X) and amine (VI) furnished the target thiourea adduct, which was finally isolated as the corresponding hydrochloride salt.

Acylation of the tertiary 20-hydroxy group of camptothecin (I) with N-Boc-valine-N-carboxyanhydride (II) afforded the corresponding ester (III). Subsequent acidic N-Boc group cleavage gave amino ester (IV). This was coupled with N-Boc-histidine (V) to furnish, after treatment with trifluoroacetic acid, the histidyl-valyl camptothecin ester (VI).

Regioselective O-methylation of p-nitrophenyl-beta-L-fucopyranoside (VII) by means of dibutyltin oxide and iodomethane provided the 3-O-methyl pyranoside (VIII). Subsequent catalytic hydrogenation of the nitro group of (VIII) over PtO2 gave aniline (IX), which was further converted to the isothiocyanate (X) upon treatment with thiophosgene and ethyl diisopropylamine. Finally, coupling between isothiocyanate (X) and amine (VI) furnished the target thiourea adduct, which was finally isolated as the corresponding hydrochloride salt.