Structure of the vitamin D 2 -tetracyanoethylene adduct.

Since chemical methods so far proposed for vitamins D determination commonly suffer from coexistence of interfering substances and hence from requirement of designing tedious purifica tion steps, a more simple analytical procedure without such pre-treatment has been strongly desired. During the course of our study on a gas-liquid chromatographic determination of vitamins D (1), efforts were also concentrated on applying other techniques of recent instru mental analysis. Recently we established a simple determination method of vitamin D2 (alternately of vitamin D3) by mass spectroscopy adopting the vitamin D2-tetracyanoethylene (TCNE) adduct as an analytical form and the vitamin D3-TCNE adduct as an internal stan dard2. We now report that the title adduct, a key substance in our new method, is composed primarily of two compounds A and B (ca. 7:10) and their structures should be represented by