Chem. Pharm. Bull. 55(7) 1079—1081 (2007)

and their glycosides are normally 22R configuration. On the other hand, spirosolanes such as tomatidine, solasodine and their glycosides take both 22R and 22S configurations (Chart 1). To determine the configuration at C-22 is very important, because the difference in C-22 configuration relates to the chemical reactions and bio-activity, for example, as shown in the following reaction of spirosolane derivatives. Esculeogenin A with a 22S configuration isolated from ripe tomato fruits was easily converted to a pregnane derivative, 3b ,16bdihydroxy-(5a)-pregn-20-one, by reaction with pyridine and water, while isoesculeogenin A with a 22R configuration also obtained from tomato fruits, was transferred into esculeogenin B by refluxing with pyridine and water (Chart 2). Generally, it is very crucial for determing the configurations at C-22 of spirostane and spirosolane derivatives; however, it has become apparent that the C-23-hydroxyspirostane and hydroxyspirosolane derivatives are conventionally decided based on the Hand C-NMR spectroscopies. This paper describes how to decide their configuration at C-22. In spirostane derivatives, the signals due to the H3-21 and H-16 of 23S-hydroxydiosgenin appeared at d 1.18 (3H, d, J 6.7 Hz) and 4.64 (1H, dd, J 7.6, 15.6 Hz), respectively; on the other hand, those in (22R,23S,25S)-3b ,6a ,23-trihydroxy-(5a)-spirostane, torvogenin, appeared at d 1.52 (3H, d, J 7.3 Hz) and d 5.22 (1H, dd, J 4.1, 13.2 Hz), respectively. The signal assigned to the H-16 in the 22R (22-b-O-) Distinction of Absolute Configuration at C-22 of C-23-Hydroxyspirostane and C-23-Hydroxyspirosolane Glycosides