Three-component, room temperature crotylation catalyzed by solid-supported Brønsted acid: enantioselective synthesis of homoallylic carbamates

[reaction: see text] A heterogeneous, three-component crotylation of in situ generated N-acyl iminium ions has been developed. This reaction proceeds under ambient temperature in MeCN and is catalyzed by macroporous polystyrene-bound sulfonic acid (MP-TsOH). Workup is accomplished by filtration, upon which the catalyst is recoverable. A range of homoallylic amine equivalents have been prepared from the corresponding aldehydes, carbamates, and chiral (E)-crotylsilanes in a highly stereoselective manner.     

New horizons in mouse immunoinformatics: reliable in silico prediction of mouse class I histocompatibility major complex peptide binding affinity

Quantitative structure-activity relationship (QSAR) analysis is a main cornerstone of modern informatic disciplines. Predictive computational models, based on QSAR technology, of peptide-major histocompatibility complex (MHC) binding affinity have now become a vital component of modern day computational immunovaccinology. Historically, such approaches have been built around semi-qualitative, classification methods, but these are now giving way to quantitative regression methods. The additive method, an established immunoinformatics technique for the quantitative prediction of peptide-protein affinity, was used here to identify the sequence dependence of peptide binding specificity for three mouse class I MHC alleles: H2-D(b), H2-K(b) and H2-K(k). As we show, in terms of reliability the resulting models represent a significant advance on existing methods. They can be used for the accurate prediction of T-cell epitopes and are freely available online ( http://www.jenner.ac.uk/MHCPred).     

Highly stereoselective intermolecular oxy-michael addition reaction to alpha,beta-unsaturated malonate esters

[reaction: see text] The highly diastereoselective oxy-Michael addition of the "naked" anion of (6S)-methyl delta lactol to alkylidiene-, arylidene-, and heteroarylidenemalonate derivatives leading to the direct formation of THP-protected beta-hydroxy ester derivatives is described. Subsequent acid-mediated deprotection affords the enantioenriched aldol products in quantitative yields.     

CamTHP*OH: a camphor-derived delta-lactol auxiliary for the effective desymmetrization of attached glycinamide residues. Asymmetric synthesis of alpha-amino carbonyl compounds

Stereoselective allylation of camphor and subsequent terminal hydroformylation affords a new delta-lactol auxiliary (camTHP*OH) on multigram scale. Stereoselective condensation with glycine dimethylamide and Cbz protection affords a camTHP*-desymmetrized glycinamide building block which undergoes efficient and highly diastereoselective metal enolate alkylation reactions. Acid-mediated deprotection affords the N-Cbz-protected alpha-amino amide products which may be converted directly to alpha-amino ketones on treatment with Grignard or organolithium reagents without loss of stereochemical integrity. [reaction: see text]     

Brauer Group Invariants Associated to Orthogonal Epsilon-Constants

In this paper, the theory of -constants associated to tame finitegroup actions on arithmetic surfaces is used to define a Brauergroup invariant µ(X, G, V) associated to certain symplecticmotives of weight one. The relationship between this invariantand w₂() (the Galois-theoretic invariant associated to tamecovers of surfaces defined by Cassou-Noguès, Erez andTaylor) is also discussed. 2000 Mathematics Subject Classification11G35 (primary), 11G40, 14G40 (secondary).     

Multicomponent gap solitons in superposed grating structures

We demonstrate, numerically, the existence and stability of multicomponent gap solitons in a Kerr nonlinear medium with a superposed grating based on a derived system of coupled-mode equations. Applications to all-optical logic and signal processing are discussed.     

On a singular behavior of capillary surfaces

Mario Miranda raised the question, whether a capillary tube of section in an infinite bath under a uniform downward gravity field always raises liquid higher over its section than does a tube of the same material and section . Finn and Kosmodemyanskii, Jr. recently gave conditions under which a negative answer is obtained for all gravity small enough; they gave also an example in which is a disk and in which the answer changes in a discontinuous way, for fixed and differentiable change of . In the present work we characterize the most general convex for which such a discontinuous change can occur.Received: 3 September 2002, Accepted: 23 January 2003, Published online: 1 July 2003Mathematics Subject Classification: 76B45, S3A10, 49Q10     

Call for Papers: Bayesian Inference for Stochastic Processes

Call for Papers

Call for Papers: Bayesian Inference for Stochastic Processes     

Combining Independent Information in a Multivariate Calibration Problem

The problem of combining independent information from different sources in a multivariate calibration setup is considered. The dimensions of the response vectors from various sources may be unequal. A linear combination of the classical estimators based on the individual sources is proposed as an estimator for the unknown explanatory variable. It is shown that the combined estimator has finite mean provided the sum of the dimensions of the response vectors exceeds one and has finite mean squared error if it exceeds two. Expressions for asymptotic bias and mean squared error are given.     

A novel site of adult doublecortin expression: neuropeptide neurons within the suprachiasmatic nucleus circadian clock

Background  

The mammalian suprachiasmatic nucleus (SCN) is composed of heterogeneous sub-groups of neurons that are organized into a neural system for the control of circadian physiology and behaviour. Molecular circadian 'clocks' are not an exclusive property of SCN neurons but the unique role of the SCN as a central integrative pacemaker is associated with specialized aspects of neuronal organization. Current studies are aimed at identifying the functional components of this hypothalamic integrative centre.