19-Norspiroxenone 2',3'-alpha-Tetrahydrofuran-2'-spiro-17-(estr-4-en-3-one) 52-02-8 Furanestrenone NSC 89030 SC 13664 Spiro(estr-4-ene-17,2'(3'H)-furan)-3-one, 4',5'-dihydro-