Cucurbiturils mimicked by low polarizability solvents with pre-formed cavities: an empirical model to predict hydrocarbon selectivity.

Relative binding affinities of a series of nine rigid hydrocarbons towards the cavity formed by a portion of the inner wall of cucurbit[8]uril (CB[8]) and a positive auxiliary guest were determined by competitive F NMR titrations in deuterium oxide. The corresponding free binding energies were corrected by the hydrocarbon computed solvation energies to obtain their free energies of transfer from the gas phase to the CB[8]/auxiliary guest cavity. These energies correlate linearly with the hydrocarbon static polarizabilities, thereby suggesting that the selectivity is driven, perhaps exclusively, by dispersive interactions between the hydrocarbons and the tailor-made cavity, regardless of the degree of unsaturation of the guests.

Enhanced photoreduction of water catalyzed by a cucurbit[8]uril-secured platinum dimer.

A cucurbit[8]uril (CB[8])-secured platinum terpyridyl chloride dimer was used as a photosensitizer and hydrogen-evolving catalyst for the photoreduction of water. Volumes of produced hydrogen were up to 25 and 6 times larger than those obtained with the corresponding free and cucurbit[7]uril-bound platinum monomer, respectively, at equal Pt concentration. The thermodynamics of the proton-coupled electron transfer from the Pt(ii)-Pt(ii) dimer to the corresponding Pt(ii)-Pt(iii)-H hydride key intermediate, as quantified by density functional theory, suggest that CB[8] secures the Pt(ii)-Pt(ii) dimer in a particularly reactive conformation that promotes hydrogen formation.

Counterintuitive torsional barriers controlled by hydrogen bonding.

The torsional barriers along the Caryl-Caryl axis of a pair of isosteric disubstituted biphenyls were determined by variable temperature 1H NMR spectroscopy in three solvents with contrasted hydrogen bond accepting abilities (1,1,2,2-tetrachloroethane-d2, nitrobenzene-d5 and dimethyl sulfoxide-d6). One of the biphenyl scaffolds was substituted at its ortho and ortho' positions with N'-acylcarbohydrazide groups that could engage in a pair of intramolecular N-HO=C hydrogen bonding interactions at the ground state, but not at the transition state of the torsional isomerization pathway. The torsional barrier of this biphenyl was exceedingly low despite the presence of the hydrogen bonds (16.

Probing Interactions between Hydrocarbons and Auxiliary Guests inside Cucurbit[8]uril.

The affinities of 20 hydrocarbons for the cavity formed by the inner wall of cucurbit[8]uril and a tolyl unit linked to an auxiliary guest were measured in aqueous solution. Cucurbit[8]uril and the auxiliary guest, a substituted ruthenium tris(2,2'-bipyridyl) complex bearing a trifluoromethyl F NMR probe, displayed perfect selectivity toward cyclic hydrocarbons, and cis- and trans-decalin, in particular. Unlike π-π interactions, CH-π interactions, as well as differences in hydrocarbon solvation, contribute significantly to the recognition process.

A New Subtype of Lichen Planopilaris Affecting Vellus Hairs and Clinically Mimicking Androgenetic Alopecia.

Background: Lichen planopilaris (LPP) is a follicular variant of lichen planus. A new subtype of LPP mimicking androgenetic alopecia (AGA) may be misdiagnosed. Inappropriate medical therapy or hair transplantation may exacerbate this subtype.

Quantitative assessment of retrograde ejaculation using semen analysis, comparison with a standardized qualitative questionnaire, and investigating the impact of rhBMP-2.

Study Design: This was a prospective study evaluating the incidence of retrograde ejaculation (RE) after anterior lumbar interbody fusion (ALIF) based on laboratory analysis of semen and urine.

Objective: The purpose of this study was to investigate the incidence of RE based on quantitative semen analysis and to compare the rate with that identified using a standardized qualitative questionnaire administered by telephone.

Summary Of Background Data: RE is a specific sexual dysfunction in which semen passes into the bladder during ejaculation.

Hormone therapy and the progression of coronary-artery atherosclerosis in postmenopausal women.

Background: In postmenopausal women with coronary artery disease, conjugated equine estrogen with or without continuous administration of medroxyprogesterone acetate has failed to slow the progression of atherosclerosis. Whether 17beta-estradiol (the endogenous estrogen molecule) alone or administered sequentially with medroxyprogesterone acetate can slow the progression of atherosclerosis is unknown.

Methods: We conducted a double-blind, placebo-controlled trial in 226 postmenopausal women (mean age, 63.