6-Methoxytryptamine (I) was condensed with methyl chloroformate to give carbamate (II), and further alkylation with benzyl bromide yielded the N-benzyl indole (III). Oxidation of the indole ring of (III) with DMSO/HCl gave oxindole (IV). Phase-transfer methylation using iodomethane and benzyltrimethylammonium bromide afforded the racemic methyl derivative (Va-b). Subsequent reduction and cyclization of (Va-b) by means of Red-Al furnished the tricyclic compound (VIa-b), which was resolved with dibenzoyl D-tartaric acid to provide the (3aS)-enantiomer (VII). Conversion of (VII) to the N,N'-dibenzyl analogue (XI) was achieved via quaternization to the ammonium salt (VIII) with iodomethane in Et2O. Ring-opening of (VIII) under basic conditions produced the hydroxy tryptamine (IX), which was again quaternized to (X) with iodomethane and then cyclized with benzylamine to provide directly the dibenzyl compound (XI). Ether cleavage of (XI) with boron tribromide gave the phenolic derivative (XII). This was coupled with 4-isopropylphenyl isocyanate in the presence of a catalytic amount of Na to yield carbamate (XIV). Finally, hydrogenolytic cleavage of the benzyl groups of (XIV) over Pd(OH)2 furnished the title compound.

6-Methoxytryptamine (I) was condensed with methyl chloroformate to give carbamate (II), and further alkylation with benzyl bromide yielded the N-benzyl indole (III). Oxidation of the indole ring of (III) with DMSO/HCl gave oxindole (IV). Phase-transfer methylation using iodomethane and benzyltrimethylammonium bromide afforded the racemic methyl derivative (Va-b). Subsequent reduction and cyclization of (Va-b) by means of Red-Al furnished the tricyclic compound (VIa-b), which was resolved with dibenzoyl D-tartaric acid to provide the (3aS)-enantiomer (VII). Conversion of (VII) to the N,N'-dibenzyl analogue (XI) was achieved via quaternization to the ammonium salt (VIII) with iodomethane in Et2O. Ring-opening of (VIII) under basic conditions produced the hydroxy tryptamine (IX), which was again quaternized to (X) with iodomethane and then cyclized with benzylamine to provide directly the dibenzyl compound (XI). Ether cleavage of (XI) with boron tribromide gave the phenolic derivative (XII). This was coupled with 4-isopropylphenyl isocyanate in the presence of a catalytic amount of Na to yield carbamate (XIV). Finally, hydrogenolytic cleavage of the benzyl groups of (XIV) over Pd(OH)2 furnished the title compound.

6-Methoxytryptamine (I) was condensed with methyl chloroformate to give carbamate (II), and further alkylation with benzyl bromide yielded the N-benzyl indole (III). Oxidation of the indole ring of (III) with DMSO/HCl gave oxindole (IV). Phase-transfer methylation using iodomethane and benzyltrimethylammonium bromide afforded the racemic methyl derivative (Va-b). Subsequent reduction and cyclization of (Va-b) by means of Red-Al furnished the tricyclic compound (VIa-b), which was resolved with dibenzoyl D-tartaric acid to provide the (3aS)-enantiomer (VII). Conversion of (VII) to the N,N'-dibenzyl analogue (XI) was achieved via quaternization to the ammonium salt (VIII) with iodomethane in Et2O. Ring-opening of (VIII) under basic conditions produced the hydroxy tryptamine (IX), which was again quaternized to (X) with iodomethane and then cyclized with benzylamine to provide directly the dibenzyl compound (XI). Ether cleavage of (XI) with boron tribromide gave the phenolic derivative (XII). This was coupled with 4-isopropylphenyl isocyanate in the presence of a catalytic amount of Na to yield carbamate (XIV). Finally, hydrogenolytic cleavage of the benzyl groups of (XIV) over Pd(OH)2 furnished the title compound.

6-Methoxytryptamine (I) was condensed with methyl chloroformate to give carbamate (II), and further alkylation with benzyl bromide yielded the N-benzyl indole (III). Oxidation of the indole ring of (III) with DMSO/HCl gave oxindole (IV). Phase-transfer methylation using iodomethane and benzyltrimethylammonium bromide afforded the racemic methyl derivative (Va-b). Subsequent reduction and cyclization of (Va-b) by means of Red-Al furnished the tricyclic compound (VIa-b), which was resolved with dibenzoyl D-tartaric acid to provide the (3aS)-enantiomer (VII). Conversion of (VII) to the N,N'-dibenzyl analogue (XI) was achieved via quaternization to the ammonium salt (VIII) with iodomethane in Et2O. Ring-opening of (VIII) under basic conditions produced the hydroxy tryptamine (IX), which was again quaternized to (X) with iodomethane and then cyclized with benzylamine to provide directly the dibenzyl compound (XI). Ether cleavage of (XI) with boron tribromide gave the phenolic derivative (XII). This was coupled with 4-isopropylphenyl isocyanate in the presence of a catalytic amount of Na to yield carbamate (XIV). Finally, hydrogenolytic cleavage of the benzyl groups of (XIV) over Pd(OH)2 furnished the title compound.