you may have a look at the following article:
Spin-Spin Coupling Constants between Carbons separated by more than one
bond
by Krivdin et al, Progr. NMR Spectr. 23 (1991), 301ff.
Best regards,
Oliver
-- ***************************** Dr. Oliver Zerbe Department of Applied Biosciences ETH Zurich Winterthurerstr. 190 CH-8057 Zurich Tel: 0041-1-635 60 81 Fax: 0041-1-635 68 84 mailto: oz@pharma.ethz.ch http://www.pharma.ethz.ch/~oz *****************************