α-Amidoboronate esters by amide-directed alkane CH borylation

α-Amidoboronic acids have received significant attention in recent years following the development of Bortezomib as an FDA-approved treatment of multiple myeloma and mantle cell lymphoma. More versatile methods to access α-amidoboronic acids continue to be developed. A direct method to access the precursors, α-amidoboronate esters, by iridium-catalyzed CH borylation of amides was developed using a readily available ligand/catalyst combination. Although the scope is limited, good yields of α-amidoboronate esters are achieved in high selectivity. Conversion of the boronate esters to the corresponding α-amidoboronic acids was also demonstrated.     

Stereoselective gamma-lactam synthesis via palladium-catalysed intramolecular allylation

A novel route to the synthesis of 3-(tolylsulfonyl)-4,5-cis-disubstituted gamma-lactams using a diastereoselective palladium-catalysed intramolecular allylation of amino acid-derived allylic carbonates has been developed.     

The cartesian closed bicategory of generalised species of structures

The concept of generalised species of structures between smallcategories and, correspondingly, that of generalised analyticfunctor between presheaf categories are introduced. An operationof substitution for generalised species, which is the counterpartto the composition of generalised analytic functors, is alsoput forward. These definitions encompass most notions of combinatorialspecies considered in the literature — including of courseJoyal's original notion — together with their associatedsubstitution operation. Our first main result exhibits the substitutioncalculus of generalised species as arising from a Kleisli bicategoryfor a pseudo-comonad on profunctors. Our second main resultestablishes that the bicategory of generalised species of structuresis cartesian closed.     

Susceptibility — Knight shift correlation and the band structure of VO2

The magnetic susceptibility and⁵¹V Knight shift have been measured in powdered VO₂ from the semiconductor-metal transition temperatureT _t=341°K to 478°K. The fact that both depend linearly on temperature enables the orbital and spin contributions to both quantities to be evaluated. The orbital and spin susceptibilities at 341°K are found to be 1.30±0.07 and 7.49±0.07μemu g^?1, respectively, and the corresponding shifts +0.61±0.04% and ?1.00±0.04%. The existence and magnitude of the orbital term are consistent with the currently accepted two band model of VO₂ aboveT _t.     

Measurement of total plasma and cerebrospinal fluid homocysteine by fluorescence following high-performance liquid chromatography and precolumn derivatization with o-phthaldialdehyde.

Precolumn derivatization of amino acids with o-phthaldialdehyde followed by high-performance liquid chromatographic separation and fluorescence detection is used in many clinical and experimental laboratories for the measurement of primary amino acids. This technique was adapted for the measurement of homocysteine in plasma and cerebrospinal fluid (CSF) following alkylation of the free sulphydryl group with iodoacetate. The minimum detection limits are less than 1 microM in plasma and 80 nM in CSF. Within-day and between-day coefficients of variation for plasma and for CSF are less than 10%. Values for normal plasma homocysteine range from 6.04 to 16.2 microM and for CSF from 0.28 to 0.66 microM.     

Estimation of tetrahydrobiopterin and other pterins in cerebrospinal fluid using reversed-phase high-performance liquid chromatography with electrochemical and fluorescence detection

We describe an isocratic, reversed-phase high-performance liquid chromatographic method for the simultaneous measurement of fully oxidised, dihydro- and tetrahydropterins in cerebrospinal fluid. Tetrahydrobiopterin is detected electrochemically using an ESA Coulochem detector in the redox mode. Dihydropterins are detected by fluorescence following post-column electrochemical oxidation, and fully oxidised pterins by their natural fluorescence. Apart from addition of antioxidants, no sample preparation is required. Comparison is made with methods requiring chemical oxidation for detection of tetrahydrobiopterin. Some results on children with neurological disease are presented.