31 (±)-Ochotensine及び類似化合物の全合成

抄録

The total synthesis of (±)-ochotensine (I) and (±)-ochotensimine (II) has been accomplished by a sequence of reactions including the Pictet-Spengler condensation of 4,5-methylenedioxyindan-1,2-dione (XXV) with 3-hydroxy-4-methoxy- and 3,4-dihydroxyphenethylamine, respectively. Prior to an approach to ochotensimine, an isomeric compound (IV) was first prepared as a model compound. The Pictet-Spengler condensation of the indandione (XIII) with the hydrobromide of the amine (XIV) in anhydrous ethanol gave the spiro-isoquinoline (XVII), which was O-methylated with an excess of diazomethane and N-methylated by the Eschweiler-Clarke method to yield (XIX). The Wittig reaction on (XIX) with methylenetriphenylphosphorane gave (IV). For the synthesis of ochotensimine, the indandione (XXV), which was prepared from ovanilline in twelve steps, was subjected to the same series of reactions as above. The Wittig reaction on (XXVII) gave (XXVIII) which was treated with formalin followed by sodium borohydride, to afford (±)-ochotensimine (II). Next, the Pictet-Spengler condensation of the indandione (XIII) with (XV) gave the spiro-isoquinoline (XXIX). After N-methylation, the phenolic hydroxyl group of (XXX) was protected as its methoxymethyl ether. The Wittig reaction with the protected compound (XXXI) and hydrolysis of the reaction product furnished the isomer (III) of ochotensine. In the same manner, the indandione (XXV) was condensed with (XV) to give the key intermediate (XXXIII) which was N-methylated and O-methoxymethylated. The resulting protected compound (XXXV) was then converted into the exomethylene derivative (XXXVI) and hydrolyzed with dilute hydrochloric acid to give (±)-ochotensine, identical with an authentic sample of (+)-ochotensine in spectral properties and t.l.c.