after exploring a variety of C-19 substituents. 1,2-Dehydrogenation in combination with subsequent A-ring aromatization via retro-aldol reaction provided a flexible and efficient protocol for the synthesis of estrogens. To demonstrate the utility of the protocol, pharmaceutically attractive estrogens were synthesized from easily available 19-hydroxy-4-ene-3-keto steroids.
In order to determine whether or not a 19-hydroxymethyl group of 19-hydroxyandrosta-1,4-diene-3,17-dione (2,19-hydroxy ADD), an intermediate of aromatase-catalyzed estrone formation from ADD,a suicide substrate of aromatase, is eliminated as formaldehyde, we examine chemical nature of removal of the 19-hydroxymethyl group. 19-Acetate 3 and 19-tert-butyldimethylsiloxy compound 4 are known to convert rapidly to estrone with treatment of NaOH or n-Bu4NF. Since compound 2 was unstable and unobtainable under these conditions, compounds 3 and 4 as equivalents to compound 2 were used in this study. The acetate 3 with 5 mol/l HCl in acetone and 10% KOH in MeOH along with the silyl ether 4 with 5 mol/l HCl in acetone and 1 mol/l n-Bu4NF in THF gave formaldehyde and estrone in which a ratio of the aldehyde to estrone was near 1. This result indicates that the 19-hydroxymethyl groups of compound 3 and 4 are eliminated as formaldehyde along with estrone derived from the steroid skeleton under the acid or base treatment. The findings suggest that a single hydroxylation at the 19 carbon of ADD (1) would be, chemically, all that was required for estrone formation. (C) 2008 Elsevier Inc. All rights reserved.
Templeton, John F.; Lin, Weiyang; Ling, Yangzhi, Journal of the Chemical Society. Perkin transactions I, 1997, # 14, p. 2037 - 2043
作者:Templeton, John F.、Lin, Weiyang、Ling, Yangzhi、Majgier-Baranowska, Helena、Marat, Kirk
etherification uses toxic or hardly degradable alkylating agents. An eco-friendly tandem etherification/aromatization is presented to prepare estrone 3-secondary ethers from easily available dienone 1. Three marketed 3-etherified estrogen drugs were synthesized with the method from commercial available starting material.