Catalytic, asymmetric halofunctionalization of alkenes--a critical perspective.

Despite the fact that halogenation of alkenes has been known for centuries, enantioselective variants of this reaction have only recently been developed. In the past three years, catalytic enantioselective versions of halofunctionalizations with the four common halogens have appeared and although important breakthroughs, they represent just the very beginnings of a nascent field. This Minireview provides a critical analysis of the challenges that accompany the development of general and highly enantioselective halofunctionalization reactions.

Hydride reduction of NAD+ analogues by isopropyl alcohol: kinetics, deuterium isotope effects and mechanism.

Observed pseudo-first-order rate constants (k(obs)) of the hydride-transfer reactions from isopropyl alcohol (i-PrOH) to two NAD(+) analogues, 9-phenylxanthylium ion (PhXn(+)) and 10-methylacridinium ion (MA(+)), were determined at temperatures ranging from 49 to 82 degrees C in i-PrOH containing various amounts of AN or water. Formations of the alcohol-cation ether adducts (ROPr-i) were observed as side equilibria. The equilibrium constants for the conversion of PhXn(+) to PhXnOPr-i in i-PrOH/AN (v/v = 1) were determined, and the equilibrium isotope effect (EIE = K(i-PrOH)/K(i-PrOD)) at 62 degrees C was calculated to be 2.

Analysis of pin force distributions of halo orthoses.

The halo orthosis is a medical device used to immobilize the cervical spine when an injury to the region is sustained. This device consists of a halo vest, support rods, a ring, and four pins that contact the skull. A major problem experienced with the halo is pin loosening.

Kinematic constraint analysis of halo orthoses.

A kinematic constraint analysis of the four pin halo orthosis is presented. Halo orthoses are used to immobilize the cervical spine after traumatic injury. Common halo orthoses consist of four pins, a halo ring, a vest, and support rods.

Brittle and sparse hair with normal cystine content caused by methionine deficiency?

The unusual case of an 8-year-old girl with a hair disorder is presented, characterized by brittle, short and sparse hair. On polarizing microscopy the latter reveals a "tiger tail" pattern, whereas severe cuticular defects are detected on scanning electron microscopy. The patient's hair has a normal cystine content but is completely devoid of methionine and reveals distinct changes of its visoelastic parameters.