Catalytic, asymmetric difluorination of alkenes to generate difluoromethylated stereocenters.

Difluoromethyl groups possess specific steric and electronic properties that invite their use as chemically inert surrogates of alcohols, thiols, and other polar functional groups important in a wide assortment of molecular recognition processes. We report here a method for the catalytic, asymmetric, migratory geminal difluorination of β-substituted styrenes to access a variety of products bearing difluoromethylated tertiary or quaternary stereocenters. The reaction uses commercially available reagents (m-chloroperbenzoic acid and hydrogen fluoride pyridine) and a simple chiral aryl iodide catalyst and is carried out readily on a gram scale.

Catalytic, Diastereoselective 1,2-Difluorination of Alkenes.

We describe a direct, catalytic approach to the 1,2-difluorination of alkenes. The method utilizes a nucleophilic fluoride source and an oxidant in conjunction with an aryl iodide catalyst and is applicable to alkenes with all types of substitution patterns. In general, the vicinal difluoride products are produced with high diastereoselectivities.

Concise and enantioselective total synthesis of (-)-mehranine, (-)-methylenebismehranine, and related Aspidosperma alkaloids.

We report an efficient and highly stereoselective strategy for the synthesis of Aspidosperma alkaloids based on the transannular cyclization of a chiral lactam precursor. Three new stereocenters are formed in this key step with excellent diastereoselectivity due to the conformational bias of the cyclization precursor, leading to a versatile pentacyclic intermediate. A subsequent stereoselective epoxidation followed by a mild formamide reduction enabled the first total synthesis of the Aspidosperma alkaloids (-)-mehranine and (+)-(6S,7S)-dihydroxy-N-methylaspidospermidine.

Robinson's landmark synthesis of tropinone.

The 1917 total synthesis of tropinone by Sir Robert Robinson represents a landmark achievement in organic synthesis. Decades ahead of its time in terms of its retrosynthetic logic and biomimetic approach, the elegant combination of these two elements in this synthesis continues to serve as an inspiration for the development of new and efficient strategies for complex molecule synthesis.

Synthesis of spirocyclic indolines by interruption of the Bischler-Napieralski reaction.

The development of a versatile method for the synthesis of spirocyclic pyrrolidinoindolines is discussed. Treatment of N-acyltryptamines with trifluoromethanesulfonic anhydride-2-chloropyridine reagent combination affords highly persistent spiroindoleninium ions that are subject to intra- and intermolecular addition at C2 by nucleophiles.

Biomechanical analysis of stresses to the fifth metatarsal bone during sports maneuvers: implications for fifth metatarsal fractures.

Fifth metatarsal stress fractures are an increasing problem in elite and recreational athletic populations. One possible mechanism of injury is the many bending moments applied to the fifth metatarsal during dynamic sports maneuvers involving rapid changes in direction and speed. A potentially important bending moment is loading of the base versus the head of the fifth metatarsal, which tends to cause a bending moment along the bone.

Direct dehydrative N-pyridinylation of amides.

Electrophilic activation of secondary amides with trifluoromethanesulfonic anhydride in the presence of 2-fluoropyridine followed by introduction of a pyridine N-oxide derivative and warming affords the corresponding N-pyridinyl tertiary amide derivatives. A mechanism supported by in situ monitoring and deuterium labeling experiments is discussed.

Regional foot pressure during running, cutting, jumping, and landing.

Background: Evaluating shoes during sport-related movements may provide a better assessment of plantar loads associated with repetitive injury and provide more specific data for comparing shoe cushioning characteristics.

Hypothesis: Accelerating, cutting, and jumping pressures will be higher than in straight running, differentiating regional shoe cushioning performance in sport-specific movements.

Study Design: Controlled laboratory study.

(S)-(+)-1-(2-Bromo-phen-yl)ethanol.

The title compound, C(8)H(9)BrO, crystallizes with two mol-ecules in the asymmetric unit. The structure displays O-H⋯O hydrogen bonding, generating zigzag chains evolving around a screw axis along [100].