Chiroptical properties and absolute configuration of pyrroloisoquinoline antidepressants

Circular dichroism (CD) spectra were determined for the bioactive (+)‐enantiomers of 1 · HCl, 3 · HCl, and 4 · HBr to characterize the chiroptical properties of these pyrroloisoquinoline antidepressants. The compounds showed a low‐intensity negative CD band with much fine structure between 252 and 272 nm, a medium negative CD band with fine structure between 215 and 225 nm, and a high‐intensity negative CD maximum between 198 and 203 nm. Except for amplitude variation, the three CD spectra were essentially superimposable in sign and position of the bands. The CD curves for the (−)‐enantiomers of 1 · HCl and 4 · HBr were opposite in sign and comparable within 5% to the (+)‐enantiomers. The results are consistent with the previously assigned (Maryanoff et al. J. Med. Chem. 30:1433–1454, 1987) absolute configurations of (6 S, 10b R ) for 1 and 3 , and (6 R, 10b R ) for 4 . Chirality 10:169–172, 1998. © 1998 Wiley‐Liss, Inc.