Proton-carbon NOE difference spectroscopy studies of carbon microenvironments. internuclear distances and hydrogen bonding in rifamycin S

Proton-proton distance measurement1 by (IH:IH) difference spectroscopy* and proton r e l a x a t i ~ na~r.e~ n ow well-established approaches for the study of conformation and dynamics of natural products5 and biopolymers.6 An alternative complementary approach was recently demonstrated on model compounds using ('H:l3C) NOE difference ~pectroscopy.~T his latter approach can (i) simultaneously delineate the carbon microenvironment and hence hydrogen bond pairs, (ii) yield proton-carbon distances, and (iii) provide criteria for distinguishing conformations of natural products and biopolymers.