On the structure and spectroscopic properties of two 13-hydroxysparteine epimers

The 13C and 1H NMR spectra of 13α-hydroxysparteine and 13β-hydroxysparteine in CDCl3 have permitted identification of their conformation with ring C a boat, the same as that of sparteine. Very weak hydrogen bond involving hydroxy group does not shift a possible conformation equilibrium as it occurs in 13α-hydroxy-2-oxosparteine and 13β-hydroxy-2-oxosparteine.