10459-27-5Relevant articles and documents
Autoxidation vs hydrolysis in 16α-acyloxy steroids
Slavikova, Barbora,Kasal, Alexander,Budesinsky, Milos
, p. 1125 - 1134 (2007/10/03)
Some enolizable α-hydroxy ketones are extremely susceptible to oxidation with traces of air in a reaction vessel. Autoxidation can be used in synthesis of oxo acids or diacids and their derivatives. Yet alkaline hydrolysis of the substrate is possible though under strictly air-free conditions.
Reactions of Enolizable Steroidal 4-En-3-ones and 17-Ones with Hypervalent Iodine
Numazawa, Mitsuteru,Mutsumi, Ayako,Ogata, Mieko
, p. 3381 - 3386 (2007/10/02)
Reaction of the 3-oxo-4-androsten-derivative 1 or 4 with 1.2 eq. of o-iodosylbenzoic acid in methanolic KOH gave the methoxy products, the 4-methoxide 2 or 5 and the 6β-methoxide 3 or 6, along with dehydrated compound, the 4,6-dienone 7 or 8, respectively.Treatment of the 6-methoxide 3 or 6 with trimethylsilyl iodide yielded the 5α-androstane-3,6-dioxo derivative 11 or 12 in high yield.The same hypervalent oxidation of the 17-oxo steroid 15, 18, 21 or 24 using excess iodine and a longer reaction time produced the corresponding 16α-hydroxy-17,17-dimethylacetal 16, 19,22 or 25, which was converted into the 16α-hydroxy-17-one 17, 20, 23 or 26 by treatment with diluted HCl in every case.Keywords - hypervalent iodine oxidation; o-iodosylbenzoic acid; 4-en-3-oxo steroid; 17-oxo steroid; methoxylation; dehydration; 16α-hydroxy-17,17-dimethoxy steroid; 16α-hydroxy-17-oxo steroid; 5α-saturated 3,6-dioxo steroid
Stereoselective hydrolysis of 16α-halo-17-keto steroids and long-range substitution effects on the hydrolysis of 16α-bromo-17-ketones and 2α-bromo-3-ketones
Numazawa,Ogata,Abiko,Nagaoka
, p. 403 - 410 (2007/10/02)
Epimerization of 16α-chloro- (1a), bromo- (1b), and iodo-3β-hydroxy-5-androsten-17-one (1c) by a brief treatment with 0.2 equiv NaOH in aqueous pyridine reached equilibrium between 16α- and 16β-halo ketones. 16α-/16β-Halo ketone ratios at equilibrium were 1.5 for Cl, 1.25 for Br, and 1.0 for I. Kinetic analysis showed that compounds 1a-c were stereoselectively converted to the corresponding 16α-hydroxy derivative 3 by an S(N)2 mechanism, in which the order of the apparent reactivity was Br > I > Cl. The hydrolysis of a number of 16α-bromo-17-ketones and 2α-bromo-3-ketones was carried out. The yields of the corresponding alcohols were found to depend on remote structural features in the steroids.
Stereospecific Synthesis of 16α-Hydroxy-17-oxo Steroids by Controlled Alkaline Hydrolysis of Corresponding 16-Bromo 17-Ketones and Its Reaction Mechanism
Numazawa, Mitsuteru,Nagaoka, Masao
, p. 4024 - 4029 (2007/10/02)
Synthesis of 16α-hydroxy-17-oxo steroids 3, 5b, and 3β,16α-dihydroxy-5-17-oxoandrosten-3-yl sulfate (7) from 16α-bromo-17-oxo steroids 1, 5a, and 6a and the reaction mechanism of the controlled alkaline hydrolysis are described.Treatment of the bromo ketones with NaOH in aqueous DMF gave the 16α-hydroxy 17-ketones stereoselectively in 95percent yield without formation of other ketols.The sodium salt of 3-sulfate 7 was also obtained in one step in 85percent yield from the corresponding bromo ketone (1a).Isotope-labeling experiments and time-course studies showed that equilibration between the 16-bromo epimers 1 and 2 precedes the formation of 3, in which the true intermediate is 2 and not 1, and that the ketol 3 is formed by the direct SN2 displacement of the 16β-bromine.The 16β-morpholino derivative 8 obtained by reaction of 1 with morpholine was shown to be an isomerized product of the 16α isomer which is produced also by SN2 displacement of the 16β-bromine.The mechanism of ketol rearrangement of 3 to the 17β-hydroxy-16-oxo compound 4 was found to involve a hydration to the carbonyl function.The new hydration-dehydration mechanism is proposed for the ketol rearrangement.
