José A. Salazar

Intramolecular hydrogen abstraction. Iodosobenzene diacetate, an efficient and convenient reagent for alkoxy radical generation

Photolysis of several hydroxy compounds in presence of iodosobenzene diacetate and iodine leads to alkoxy radical derivatives which undergo intramolecular hydrogen abstraction to produce cyclic ethers in good yield.

Intramolecular hydrogen abstraction. Hypervalent organoiodine compounds, convenient reagents for alkoxyl radical generation

The photolyses of 5α-cholestane-3β,6β-diol 3-acetate (1), 5α-cholestan-2β-ol (4), 5α-cholestan-4β-ol (8), (20R)-pregn-5-ene-3β,20-diol 3-acetate (19), (20S)-pregn-5-ene-3β,20-diol 3-acetate (21), and dihydrotigogenin 3-acetate (25) in the presence of iodine and various hypervalent organoiodine compounds lead to alkoxyl radicals which undergo intramolecular hydrogen abstraction to produce, in most cases, 1,4-iodohydrins and tetrahydrofuran derivatives.

Steroidal N-nitroamines. Part 4. Intramolecular functionalization of N-nitroamine radicals: synthesis of 1,4-nitroimine compounds

Photolysis of 6β-nitroamino-5α-cholestane (4), 6β-nitroamino-5α-cholestan-3β-yl-acetate (5), 2β-nitroamino-5α-cholestane (13), 4β-nitroamino-5α-cholestane (17), (20R)-20-nitroaminopregn-5-en-3β-yl acetate (26), (20R)-(31) and (20S)-(34)-nitroamino-5α-pregnan-3β-yl acetate, (23R, 25S)-3β-acetoxy-23-nitroamino-5β-spirostan (46), 3β-nitroaminofriedelane (53), and methyl 3β-nitroaminofriedelan-29-oate (54) in the presence of iodine and various oxidative reagents leads to neutral nitroaminyl radicals which undergo intramolecular hydrogen-abstraction to produce in most cases N-nitroimine compounds. Best results were obtained with the system iodine and (diacetoxyiodo) benzene.

Long-acting contraceptive agents: testosterone esters of unsaturated acids

The synthesis of 13 new esters of testosterone is described, with the esterifying acids bearing acetylenic, olefinic, or polyunsaturated functions in the chain, for evaluation as long-acting androgens.

New sources of steroid sapogenins—XIV : 25S-ruscogenin and sansevierigenin, two new spirostan sapogenins from Sansevieria trifasciata☆

Abstract From the leaves of Sansevieria trifasciata Prain β-sitosterol, ruscogenin (IIIa), neoruscogenin (Ia), and the two new spirostan sapogenins 25 S -ruscogenin (IIa) and sansevierigenin (Va) have been isolated and the structures determined by chemical and spectroscopic methods.

Ionic Liquid, Surrogate Hydrogen Bromide Reagent for Ring Opening of Cyclopropyl Ketones

Ionic liquid reagents created by addition of 1 equiv of either CF3CO2H or CF3SO3H to N-pentylpyridinium bromide exhibit excellent chemical reactivities as surrogate HBr reagents in ring-opening reactions of cyclopropyl ketones as well as of 2,2-difluorocyclopropyl ketones to form the respective 3-bromopropyl or 3-bromo-2,2-difluoropropyl ketones in good to excellent yields.

Intramolecular functionalization of amides leading to lactams

Abstract Formation of lactams is observed by photolysis of amides in the presence of the iodosobenzene diacetate/I 2 system and other oxidation agents through intramolecular functionalization of non-activated carbons involving a 1,6- or 1,5-hydrogen shift.

Nitroamine radicals as intermediates in the functionalization of non-activated carbon atoms

Photolysis of N-iodonitroamines generated in situ from the steroidal nitroamines 6β-nitroamino-5α-cholestan-3β-ol acetate, 6β-nitroamino-5α-cholestane-3β,5α-diol diacetate, and 20R-nitroaminopregn-5-en-3-ol acetate removes hydrogen atoms from the Me-18 and Me-19 groups to give 6β-,19-N-nitroepinino-5α-cholestan-3β-ol acetate, 6β,19-N-nitroepinino-5α-cholestane-3β5α-diol diacetate, and 18,20R-N-nitroepiminopregn-5-en-3β-ol acetate.

Ring expansion reactions of 1,3-dithiolans and 1,3-dithians. A new synthesis of dihydro-1,4-dithiins and dihydro-1,4-dithiepins

Abstract A mild and convenient method for ring expansion of 1,3-dithiolans and 1,3-dithians to dihydro-1,4-dithiins and dihydro-1,4-dithiepins, respectively, using phenyl selenenyl chloride in methylene chloride is described. A mechanism involving sulphenyl chloride derivatives as intermediates is proposed.

Iguesterin, a new quinonoid triterpene from Catha cassinoides

Abstract β-Amyrin, sitosterol, celastrol, pristimerin, tingenone and a new hydroxymethylene quinonoid dinor-triterpene iguesterine were isolated from the root bark of Catha cassinoides. The structure of iguesterine was determined spectroscopically and by synthesis from tingenone. Tentative assignments are given for the chemical shifts of the methyl groups of iguesterin, tingenone and some of their derivatives.