The chiral intermediate (S)-alpha-methyl-1,3-benzodioxole-5-ethanol (IV) was prepared by microbiological reduction of 3,4-methylenedioxyphenyl acetone (I) or, alternatively, by lithiation of 4-bromo-1,2-(methylenedioxy)benzene (II) with sec-butyllithium, followed by addition to (S)-propylene oxide (III). Hydrochloric acid-promoted condensation of (IV) with p-nitrobenzaldehyde (V) in hot toluene gave rise to the dioxolobenzopyran system (VIa-b), which was hydroxylated to (VIIa-b) by air oxidation under alkaline conditions. Hydrazone (IXa-b) was obtained as a mixture of E,Z isomers upon treatment of (VIIa-b) with 2-hydrazinopyridine (VIII) in refluxing EtOH. After mesylation of the alcohol group of (IXa-b) with methanesulfonyl chloride and triethylamine, the resulting mesylate (Xa-b) was cyclized to the dioxolo benzodiazepine (XI) using lithium tert-butoxide in THF. The nitro group of (XI) was finally reduced to the target aniline by transfer hydrogenation with potassium formate in the presence of Pd/C.

The chiral intermediate (S)-alpha-methyl-1,3-benzodioxole-5-ethanol (IV) was prepared by microbiological reduction of 3,4-methylenedioxyphenyl acetone (I) or, alternatively, by lithiation of 4-bromo-1,2-(methylenedioxy)benzene (II) with sec-butyllithium, followed by addition to (S)-propylene oxide (III). Hydrochloric acid-promoted condensation of (IV) with p-nitrobenzaldehyde (V) in hot toluene gave rise to the dioxolobenzopyran system (VIa-b), which was hydroxylated to (VIIa-b) by air oxidation under alkaline conditions. Hydrazone (IXa-b) was obtained as a mixture of E,Z isomers upon treatment of (VIIa-b) with 2-hydrazinopyridine (VIII) in refluxing EtOH. After mesylation of the alcohol group of (IXa-b) with methanesulfonyl chloride and triethylamine, the resulting mesylate (Xa-b) was cyclized to the dioxolo benzodiazepine (XI) using lithium tert-butoxide in THF. The nitro group of (XI) was finally reduced to the target aniline by transfer hydrogenation with potassium formate in the presence of Pd/C.