Stereochemistry of the methylidene-bridged quinazoline-isoquinoline alkaloid 3-{[6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinolin-2-yl]methylidene}-1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-9-one methanol monosolvate

Abstract

Two potentially bioactive fragments, namely a tricyclic quinazoline derivative with an exocyclic alkene moiety and a substituted isoquinoline, are coupled to give 3-{[6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinolin-2-yl]methylidene}-1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-9-one. The target product crystallizes as a methanol solvate, C29H26N4O5·CH4O, and is E configured. The alternative Z isomer would necessarily imply either considerable twist about the central double bond or very unfavourable intramolecular contacts between sterically more demanding substituents. The main residue and the co-crystallized solvent molecule aggregate to discrete pairs via a classical O—H...O hydrogen bond with a distance of 2.8581 (7) Å between the methanol OH donor and the quinazolinone O=C acceptor.

Keywords

• quinazoline
• isoquinoline
• steric congestion
• hydrogen bonding
• crystal structure