1,1-Di(9-fluorenyl)ethanol, a by-product from the acetylation of 9-fluorenyllithium

Treatment of 9-fluorenyllithium with acetyl chloride produces 9-acetylfluorene, (I), and several by-products. Among them is a compound unequivocally identified for the first time as the addition product of (I) with 9-fluorenyllithium, 1,1-di(9-fluorenyl)ethanol, C(28)H(22)O, (II). The two fluorene-ring planes of (II) are essentially perpendicular [89.90 (9) degrees ]. A number of intermolecular non-bonding distances are well within or close to the sum of their respective van der Waals radii and may be responsible for the rarely observed large bowing of one of the fluorene rings. This bowing apparently arises from two molecules impinging on the convex face of the bowed ring, augmented by hydrogen bonding between the peripheral pi electrons of the concave face and the hydroxyl H atom of another molecule adjacent to that face.

1,1-Di(9-fluorenyl)ethyl acetate, a by-product from the acetylation of 9-fluorenyllithium

The preparation of sp-9-acetylfluorene from the reaction of 9-fluorenyllithium with acetyl chloride also provided 9-(1-acetoxyethylidene)fluorene ('diacetylfluorene') and 1,1-di(9-fluorenyl)ethanol, (II), as by-products recently characterized by X-ray analysis. A third by-product, 1,1-di(9-fluorenyl)ethyl acetate, (III), C(30)H(24)O(2), has now been unequivocally identified for the first time, and emanates from the acetylation of the oxyanion of (II). In the asymmetric unit, compound (III) exists as two almost identical structures which differ slightly, but significantly, in conformation. Neither possesses the significant fluorene-ring bowing or the perpendicularity of the two ring planes exhibited by (II). The angle between the least-squares planes of the two fluorene rings of (III) is 58.45 (9) and 60.95 (10) degrees, respectively, for the two conformations, and their corresponding bonding parameters also differ slightly in a number of instances.

9-(1-Acetoxyethylidene)fluorene ("diacetylfluorene"), a by-product from the acetylation of 9-fluorenyllithium

Treatment of 9-fluorenyllithium with acetyl chloride produces 9-acetylfluorene, (I), and several by-products, among which is "diacetylfluorene", now characterized definitively as 9-(1-acetoxyethylidene)fluorene [IUPAC name: (1-fluoren-9-ylidene)ethyl acetate], (II), C(17)H(14)O(2), derived from acetylation of initially formed (I). Various parameters disclose substantial structural distortion within (II) emanating from A((1,3)) strain associated with the 9-(acetoxyethylidenyl)fluorene system.

Unexpected dipivaloylation of 9-lithiated fluorene: formation of 1-(fluoren-9-ylidene)-2,2-dimethylpropyl pivalate

Treatment of 9-lithiated fluorene with pivaloyl chloride provided ap-9-pivaloylfluorene, (1), the major product, and a minor product ultimately identified as the title compound, C(23)H(26)O(2), (2). The latter was also formed directly, but slowly, from 9-lithiated-(1) treated with pivaloyl chloride. Although (1) exists exclusively as its less sterically restricted ap rotamer, its sp(2)-hybridized anion sterically impedes reaction at the 9-position from either face. While 9-lithiated-(1) is exclusively, but slowly, 9-methylated with methyl iodide, reaction with pivaloyl chloride, also slow, leads only to the O-acylated product, (2). The protons of the tert-butyl-C=C moiety approach a proton on the fluorene ring to well within the sum of their van der Waals radii, resulting in significant molecular compression, strain and distortion. For example, distortion in the moiety C=C(O)(C) is exhibited by the enlargement of C=C-C angle to 130.6 (2) degrees at the expense of the corresponding 'equivalent' C=C-O angle, which is compressed to 116.46 (19) degrees.

Transcriptional regulation of estrogen-responsive genes by non-steroidal estrogens: doisynolic and allenolic acids

Estrogen receptor (ER), a member of the nuclear receptor superfamily, exerts prominent physiological roles in both humans and other species by acting directly as a transcription factor, altering nuclear gene expression. One peculiarity of estrogenic regulation is that it is affected by a wide variety of non-steroidal compounds in addition to the natural hormone, estradiol. Doisynolic and allenolic acid compounds are non-steroidal compounds that act as potent estrogens in animal studies, yet bind to ER extremely poorly in competitive binding assays, raising the possibility of alternative molecular mechanisms for the observed estrogenic effects. In this work we demonstrate that (+/-)-Z-bisdehydrodoisynolic acid, (+/-)-Z-bisdehydrodoisynolic acid 3-methyl ether, and (-) allenolic acid can interact directly with ER. These compounds all serve as ligands for ER in mechanism-specific tissue culture-based reporter gene assays for both positive and negative gene regulation. We have also used a novel assay based on electromobility shift by ER for directly determining relative binding affinities for ER. In addition, we show cell-type-specific activity differences for (+/-)-Z-bisdehydrodoisynolic acid 3-methyl ether, supporting clinical observations indicating a higher potency of this compound in female animals than in humans.