This paper describes the preparation and properties of a number of 20/3,25d-and 20/3,25L-sapogenins. The latter are characterized by being much more dextrorotatory than their 25o-analogs. Both series have infrared spectra which differ from each other and from those of the analogous 20a-compounds. Sapogenins of the 20/3-series are characterized by a spiroketal side chain which is much more labile than the 20a-series. Thus the latter group is not attacked by mild CrOs oxidation. Sapogenins of the 20/3,25L-series are cleaved to acidic intermediates which on alkaline treatment yield Als-20-ketopregnenes. Compounds of the 20/3,25D-group behave similarly, but in addition also yield on oxidation a new group of sapogenins which contain an additional hydroxyl tentatively placed at C2o. 20-isohecogenin is an exception and forms only the hydroxylated derivative. The cleavage fragments of 20/3,25l-and 20/3,25D-sapogenins gave ( + )-and (-)-a-methylglutaric acids, thus establishing the C26-configuration of both groups.

The rearrangement of fatty epoxyesters to ketoesters was studied. The isomerization is carried out in nonaqueous media and is catalyzed by acids. Esters containing one epoxy group per fatty acid chain are isomerized to the corresponding ketones in 70舑90% yields using boron fluoride etherate catalyst in boiling dioxane. Conversion to ketonic products is measured either by chromatographic separation followed by IR analysis or by oximation. Principal byproducts are hydroxy derivatives. Fatty esters containing more than one epoxy group/fatty acid chain give low ketone yields.

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