Dehydrative reduction: a highly diastereoselective synthesis of syn-bisaryl(or heteroaryl) dihydrobenzoxathiins and benzodioxane

A Straightforward Route to Potent Phenolic Chain-Breaking Antioxidants by Acid-Promoted Transposition of 1,4-Benzo[b]oxathiines to Dihydrobenzo[b]thiophenes

The transformation of simple phenols with limited antioxidant activity into potent chain-breaking antioxidants was achieved by a three-step protocol, consisting of the conversion of phenols into 1,4-benzo[b]oxathiines followed by an unprecedented acid-promoted transposition to o-hydroxydihydrobenzo[b]thiophenes, or dihydrobenzo[de]thiochromenes, starting from phenols or naphthols, respectively. These derivatives, bearing a benzo-fused heterocycle with a sulfide sulfur ortho to the phenolic OH, have a rate constant of reaction with alkylperoxyl radicals (kinh ) comparable to that of α-tocopherol. A solid rationale for the transposition mechanism as well as for the structure-antioxidant activity relationship is presented.

Recent progress towards ionic hydrogenation: Lewis acid catalyzed hydrogenation using organosilanes as donors of hydride ions

Recent advances in ionic hydrogenation as well as its fundamental mechanism are summarized and discussed.

Copper-catalyzed tandem process: an efficient approach to 2-substituted-1,4-benzodioxanes

An efficient method for the preparation of various 2-substituted-1,4-benzodioxanes by CuBr-catalyzed tandem reactions of 2-((o-iodophenoxy)methyl)oxiranes with phenols has been developed. The reaction involves the ring-opening process of 2-((2-iodophenoxy)methyl)oxirane followed by an intramolecular C-O cross coupling cyclization.

Estrogen receptor ligands. Part 5: The SAR of dihydrobenzoxathiins containing modified basic side chains

Dihydrobenzoxathiin analogs (1-11) with modifications on the basic side chain region were prepared and evaluated for estrogen/anti-estrogen activity in both in vitro and in vivo models. The compounds generally maintained a high degree of selectivity for ERalpha over ERbeta, similar to the original lead compound I. Many of the compounds also maintained high potency in the inhibition of human carcinoma MCF-7 cell growth. However, all were less potent in the inhibition of estradiol-triggered uterine growth. This work demonstrates the sensitive nature of modification to the antagonist basic side chain region.

Estrogen receptor ligands. Part 6: Synthesis and binding affinity of dihydrobenzodithiins

Dihydrobenzodithiin compounds (1-6) were prepared to explore the expansion of the dihydrobenzoxathiin lead compounds I-III as SERAMs (Selective Estrogen Receptor Alpha Modulators). The dihydrobenzodithiin compounds generally maintained a high degree of selectivity for ERalpha over ERbeta, however, they lacked the in vivo antagonism/agonism activity exhibited by the lead class in an immature rat uterine growth model.

Estrogen receptor ligands. Part 11: Synthesis and activity of isochromans and isothiochromans

The ring oxygen and sulfur analogs of lasofoxifene, 1a and 1b, were synthesized in an attempt to impart ERalpha selectivity, as found in the closely related dihydrobenzoxathiin compound I, recently discovered in these laboratories. The resulting isochroman and isothiochroman compounds were found to exhibit equipotent binding affinities to the ER isoforms and were less active in the inhibition of estradiol-triggered uterine growth when compared to I and lasofoxifene.

Estrogen Receptor Ligands. 12. Synthesis of the Major Metabolites of an ERα-Selective, Dihydrobenzoxathiin Antagonist for Osteoporosis

[reaction: see text] During the course of drug metabolism studies, a major metabolite of compound 1 was detected in rhesus monkeys and assigned structure 4. The intriguing biotransformation of 1 leading to 4 was confirmed by a 19-step total synthesis starting from resorcinol (11), the key feature of which was the construction of the oxygen bridge utilizing a phenolic oxidation and trapping sequence. In addition, the synthesis of a related metabolite (5) is described.

Estrogen receptor ligands. Part 4: The SAR of the syn-dihydrobenzoxathiin SERAMs

A series of estrogen receptor ligands based on a dihydrobenzoxathiin scaffold is described and evaluated for estrogen/anti-estrogen activity in both in vitro and in vivo models. The most active analogue, 22, was found to be 40-fold ERalpha selective in a competitive binding assay, and 22 demonstrated very potent in vivo antagonism of estradiol driven proliferation in an immature rat uterine weight gain assay.

Estrogen receptor ligands. Part 3: The SAR of dihydrobenzoxathiin SERMs

A series of 3-alkyl, 3-cycloalkyl, and 3-heteroaryl dihydrobenzoxathiin analogs 1 were prepared and evaluated for estrogen/anti-estrogen activity in both in vitro and in vivo models. In general, the compounds were found to exhibit a high degree of selectivity for ER alpha over ER beta, but were less potent than the original lead compound 1a in the inhibition of estradiol-driven uterine proliferation.

An efficient asymmetric synthesis of an estrogen receptor modulator by sulfoxide-directed borane reduction

An efficient asymmetric synthesis of a selective estrogen receptor modulator (SERM) that has a dihydrobenzoxathiin core structure bearing two stereogenic centers is reported. The stereogenic centers were established by an unprecedented chiral sulfoxide-directed stereospecific reduction of an alpha,beta-unsaturated sulfoxide to the saturated sulfide in one step. Studies to elucidate the mechanism for this reduction are reported. Highly efficient Cu(I)-mediated ether formation was used to install the ether side chain, and selective debenzylation conditions were developed to remove the benzyl protecting groups on the phenols.