Synthesis of naturally occurring ecteinascidins and related compounds

A compound of formula:

• wherein
• Ra and Rb together with the carbon to which they are attached form a group of formula:
• where Rd is a substituted or unsubstituted R′, OR′, —(C═O)R′, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl;
• wherein R′ is selected from the group consisting of OH, NO2, NH2, SH, CN, halogen, C(═O)H, C(═O)CH3, CO2H, CO2CH3, C1-C6 alkyl, alkenyl, alkynyl, aryl, aralkyl and heterocyclic;
• each X1 in:
• is independently selected from hydrogen or substituted or unsubstituted R′, OR′, —(C═O)R′, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, and substituted or unsubstituted aralkyl;
• wherein R′ is selected from the group consisting of H, OH, NO2, NH2, SH, CN, halogen, C(═O)H, C(═O)CH3, CO2H, CO2CH3, C1-C6 alkyl, alkenyl, alkynyl, aryl, aralkyl and heterocyclic;
• R7 is —OCH3 and R8 is —OH or R7 and R8 together form a group —O—CH2—O—;
• R12a is hydrogen, acyl, alkenyl, or alkyl-O—CO—;
• R21 is —H, OH or CN;
• X is —O— or —NH—;
• R5 and R18 are each —OX1, wherein each X1 is independently selected from hydrogen, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, or —C(═O)R′ wherein R′ is selected from hydrogen, OH, NO2, NH2, SH, CN, halogen, C1-C6 alkyl, alkenyl, alkynyl, aryl, aralkyl, and heterocyclic.