合成路线1

2) The esterification of 2-hydroxy-3-methoxybenzaldehyde (XXIV) with methanesulfonyl chloride and triethylamine gives the corresponding mesylate (XXV), which is nitrated with fuming HNO3 to 2-(methanesulfonyloxy)-3-methoxy-6-nitrobenzaldehyde (XXVI). The condensation of (XXVI) or 2-(benzenesulfonyloxy)-3-methoxy-6-nitrobenzaldehyde (XXVIII) with 2-(diethoxyphosphoryl)acetic acid methyl ester by means of NaH in THF yields 3-(2-hydroxy-3-methoxy-6-nitrophenyl)acrylic acid methyl ester (XXVII), which is benzylated with benzyl bromide and K2CO3 to the benzyl derivative (XXIX). The cyclization of (XXIX) with refluxing triethyl phosphite affords 4-benzyloxy-5-methoxy-1H-indole-2-carboxylic acid methyl ester (XXX), which is reduced to the corresponding carbaldehyde (XXXI) according to Tetrahedron Lett 1994, 50: 7657. The methylation of (XXXI) with NaH and methyl iodide in DMF yields the N-methyl derivative (XXXII), which is condensed with 2-(diethoxyphosphoryl)acetic acid methyl ester by means of NaH in THF to afford 3-(4-benzyloxy-5-methoxy-1-methylindol-2-yl)acrylic acid methyl ester (XXXIII). The formylation of (XXXIII) with POCl3 and DMF gives the 4-formyl derivative (XXXIV), which is debenzylated with trimethylsilyl iodide in acetonitrile to the 4-hydroxy compound (XXXV). The oxidation of (XXXV) with Fremy's salt as before yields 3-(3-formyl-5-methoxy-1-methyl-4,7-dioxo-4,7-dihydro-1H-indole-2-yl) acrylic acid methyl ester (XXXVI), which is treated successively with Na2S2O4, DIBAL, and finally with FeCl3, as before, to afford the dihydroxy quinone (XXII), already obtained.