Betanidin hydrolysis

The (25) configuration of betanidin has been determined by the identification of degradation product 7 as (5)-cyclodopa (5). For the determination of the absolute configuration at C-15, studies on the stereochemical relationship of betanidin (1) and isobetanidin (6) were of importance. It was found that on hydrolysis of betanin (5) under drastic conditions (18% HCl, 87°C) the ratio of 6 to 1 formed increased with the reaction time, whereas with concentrated HCl at room temperature the aglycone contained only 5% of 6 (29). On treatment of either pure 1 or 6 with 0.4 N KOH at 25°C with exclusion of oxygen, a 1 2 equilibrium mixture of the two isomers was formed. That the epimerization takes place at C-15 is indicated by the fact that both isomers gave the same optically... 

---