(V) and tachysterol (111), both of which are convertible to vitamin D2 by further irradiati~ n.~ The isolation of an additional compound, praecalciferol, 6 present in the mixture obtained on irradiation of ergosterol, has shed some new light on the mechanism of vitamin formation. Velluz recently revealed experimental findings from which he deduced structure I1 for praecalciferol, 6 which would thus be the cis isomer of tachysterol (111). Of even greater ...
![Hydrazinecarboxamide,2-[1-methyl-3-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-propen-1-ylidene]- Structure](https://image.chemsrc.com/caspic/182/2302-89-8.png)
