CHARACTERIZATION OF THE LIGHT-MEDIATED AND BASE-MEDIATED INSTABILITY OF CALBISTRIN-A

The isolation and characterization of calbistrin A [1] were complicate d by the compound's instability. The instability was caused by light, which led to a complex degradation of 1. The nature of the light insta bility was elucidated by forming the dimethyl acetal derivative 2, whi ch isomerized upon exposure to light, leading to an equilibrium mixtur e of 2 and 3. Alkaline conditions also caused decomposition of 1, lead ing to the formation of 4.