合成路线1

Combretastatin A-4 phosphate can be synthesized by phosphorylation of combretastatin A-4 (I) following several related strategies. Direct phosphorylation of (I) employing either bis(2,2,2-trichloroethyl) phosphorochloridate in pyridine (1, 2) or dibenzyl phosphite in the presence of CCl4 and DMAP (3-5) furnishes the corresponding bis-trichloroethyl (IIa) and dibenzyl (IIb) phosphate esters, which are subsequently deprotected to combretastatin A-4 phosphate (III) by either reductive trichloroethyl group cleavage with zinc dust and acetic acid (1, 2) or by debenzylation with chlorotrimethylsilane/sodium iodide (3-5). Alternatively, phosphitylation of (I) using di-tert-butyl N,N-diethylphosphoramidite (3, 4, 6) or bis(trimethylsilylethyl) N,N-diisopropylphosphoramidite (3-5) in the presence of tetrazole yields the phosphite esters (IVa) and (IVb), respectively, which are further oxidized to the corresponding phosphates (Va) and (Vb) using m-chloroperbenzoic acid in CH2Cl2/THF (3-6). Combretastatin A-4 phosphate (III) is then obtained by acidic cleavage of the tert-butyl ester (Va) with trifluoroacetic acid (3, 4, 6) or trifluoromethanesulfonic acid (6), or by tetrabutylammonium fluoride-promoted cleavage of the trimethylsilylethyl ester (Vb) (3-5). In a shorter procedure, phosphorylation of combretastatin A-4 (I) with POCl3 in the presence of Et3N in CH2Cl2 provides directly combretastatin A-4 phosphate (III) (7). Conversion of (III) to the title disodium salt is accomplished by treatment with methanolic NaOMe (3-5,7) or by passage through a cation exchange resin (1, 2). Scheme 1.