o representing c 25 26 27 hydroxyl indicated that the product had the same side chain as its precursor but the absence of the typical vitamin d ring a fragments indicated a highly modified triene system given the presence of an u03b1 u03b2 unsaturated keto uv spectrum the unusual elimination of ch 2 o in the mass spectrum could be rationalized by assuming a 7 keto 5 en 10 hydroxymethyl system a structural arrangement which allows for the loss of the hydroxymethyl group as ch 2 o by the well known mclafferty rearrangement process the high resolution nuclear magnetic resonance spectrum 270 mhz in cdcl 3 of the compound provided conclusive proof of structure a one proton singlet was observed at u03b45 26 as the only signal in the olephinic proton region u03b45 7 thus there is only one isolated olefinic proton two one proton doublet of doublets at u03b43 62 and u03b43 39 with coupling constants of 14 and 7 hz establish the presence of a 10 hydroxymethyl function c 19 these signals represent the protons on c 19 coupled to each other 14 hz and to a third proton at c 10 7 hz in a typical abx pattern decoupling experiments employing difference double resonance spectroscopy fully confirmed this structural assignment a resonance at u03b43 6 for the 3 u03b1 carbinyl proton and the sharp singlet at u03b41 21 for the c 26 27 methyl groups confirm the presence of the 3 u03b2 hydroxy and 25 hydroxy function respectively the composition of the molecule c 27 h 44 o 4 requires two double bonds one of which can be assigned to the c 5 6 position thus.