STUDIES OF FUSED RING SYSTEMS I.REACTION OF 7-METHOXY-1-KETO-2-METHYL-1,2,3,4-TETRAHYDROPHENANTHRENE WITH METHYL γ-BROMOCROTONATE;SYNTHESIS OF DL-HOMOEQUILENIN AND DEGRADATION OF ITS METHYL ETHER INTO DL-EQUILENIN