[CH3:1][C:2]1[C:22](=O)[C:20](=[O:21])[C:5]2[C@@H:6]([CH2:15][O:16][C:17]([NH2:19])=[O:18])[C@@:7]3([O:13][CH3:14])[C@H:11]4[NH:12][C@H:10]4[CH2:9][N:8]3[C:4]=2[C:3]=1[OH:24].CO.P(=O)(O)(O)O.[N+:32](=C(C1C=CC=CC=1)C1C=CC=CC=1)=[N-]>C(Cl)Cl.O>[CH3:1][C:2]1[C:3](=[O:24])[C:4]2[N:8]3[C@@:7]([O:13][CH3:14])([C@H:6]([CH2:15][O:16][C:17]([NH2:19])=[O:18])[C:5]=2[C:20](=[O:21])[C:22]=1[NH2:32])[C@H:11]1[NH:12][C@H:10]1[CH2:9]3
We turn now to the case where drying (i.e., water removal) is not carried out, i.e., in the case where aqueous solution of basic 7-salt oxide-9a-methoxymitosane is treated directly with acid. The acid is preferably aqueous phosphoric acid and is admixed to provide a pH of 4.7 to 6.5, very preferably from 5 to 6, to produce aqueous solution of 7-hydroxy-9a-methoxymitosane. The reaction of this with diazodiphenylmethane proceeds as follows. The diazodiphenylmethane is admixed. The solvent in which the diazodiphenylmethane is dissolved and/or which is otherwise admixed is a solvent or solvent combination in which both the 7-hydroxy-9a-methoxymitosane and diazodiphenylmethane are soluble and preferably is the combination of methylene chloride and methanol in a volume ratio of methylene chloride to methanol ranging, for example, from 0.5:1 to 3:1. The reaction between 7-hydroxy-9a-methoxymitosane proceeds despite the presence of water apparently as an extractive alkylation where the organic solvent extracts the 7-hydroxy-9a-methoxymitosane from the water phase for reaction in organic solvent phase (preferably methylene chloride). The alkylation reaction to produce 7-(diphenylmethyl)oxy-9a-methoxymitosane proceeds, for example, at a temperature ranging from 0° C. to 30° C. for 1 to 10 hours using an excess of diazodiphenylmethane, e.g., 2 to 5 equivalents of diazodiphenylmethane. During the alkylation reaction, acid, preferably aqueous phosphoric acid, is preferably added periodically as may be necessary to maintain the pH in the range of 4.7 to 6.5, very preferably 5 to 6. When the alkylation reaction is completed, organic phase is separated and substantially pure 7-(diphenylmethyl)oxy-9a-methoxymitosane is recovered, e.g., by drying to remove water and evaporating to remove organic solvent and recovering product from the residue by chromatography on Al2O3 or SiO2. Additional product can be obtained by vigorously mixing the aqueous phase with diazodiphenylmethane in solvent for it and 7 -hydroxy-9a-methoxymitosane, preferably methylene chloride, and reacting, preferably at 15° C. to 25° C. for 10 to 20 hours, and recovering additional product, e.g., by chromatography. Yields from mitomycin C, including product obtained from workup of the aqueous phase, of 40 to 60% have been obtained. These yields are unexpected in view of the Sami, et al article referred to above.
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