Progesterone metabolite. Isoln from pregnant mares' urine: Brooks et al., Biochem. J. 51, 694 (1952). Prepn by heating 3α,20α-dihydroxy-5α-pregnane with sodium, or by hydrogenation of 5α-pregnane-20-ol-3-one in acid: Marker, US 2196220 and US 2250962 (1940, 1941, both to Parke, Davis); by reduction of allopregnan-3β-ol-20-one acetate with sodium: Klyne, Barton, J. Am. Chem. Soc. 71, 1500 (1949); by reduction of 5,16-pregnadien-3β-ol-20-one with Zn + acetic acid: Ercoli, De Ruggieri, Farm. Sci. Tec. 7, 11 (1952), C.A. 46, 10186b (1952).