Intermediate and Process of Preparation of Ecteinascidin Such As Ecteinascidines-583, 597 Using Such Intermediate

The present invention concerns an intermediate of the following formula (I) in which R1 and R2 represent independently of each other a C1-C12 alkyl group, a (C1-C12 alkoxy)carbonyl group, optionally substituted by one, two or three halogen atom, a (C2-C12 alkenyloxy) carbonyl group, an acyl group, a aryl(C1-C12)alkyl group, an arylalkoxy carbonyl group, a (C1-C12 alkyl)sulfonyl group or an arylsulfonyl group, R3 represents a O-protecting group, R4 and R5 represent independent ly of each other a hydrogen atom or a O-protecting group, R6 represent a O-protecting group and R7 represent a C1-C12 alkyl group or -OR6 and -OR7 form together a group -OCH2O-. The present invention concerns also a process of preparation of the intermediate and its use for the preparation of Ecteinascidin 743 and Ecteinascidin-770.