Changes In Conformational Equilibrium Research Articles

Steroidal sulphur compounds. Part V. Configuration, conformation, and chiroptical properties of steroidal benzyl sulphoxides

Steroidal C-3 and C-6 benzyl sulphoxides of (R)-configuration at sulphur displayed negative Cotton effects below 220 nm. and positive Cotton effects in the range 229–236 nm. in ethanol. The Cotton effects are of greater amplitude and occur at longer wavelengths than those of the corresponding methyl sulphoxides, in analogy with the relation between dialkyl and alkyl benzyl ketones. Changes in conformational equilibria were probably not important in solvent-induced variations in amplitudes of the Cotton effects. Pyrolysis of (R)-3α-benzylsulphinyl-5α-cholestane gave 5α-cholest-2-ene regiospecifically.

Correlation of specific rotation with conformation. A new approach to the study of conformational equilibria

The marked changes in optical rotation which occur on dissolving the methyl 2-deoxy-α-L-and 3-deoxy-β-L-erythro-pentopyranosides in a variety of solvents including chloroform, acetone, acetonitrile, pyridine, dimethylsulfoxide, and water were found by nuclear magnetic resonance to result almost exclusively from changes in conformational equilibria. The changes in rotation are in agreement with those expected from Brewster's rules.