Minimaxity and nonminimaxity of a preliminary test estimator for the multivariate normal mean

Summary The problem is to estimate the mean of ap-dimensional normal distribution in the situation where there is vague information that the mean vector might be equal to zero vector. Minimax property of the preliminary test estimator obtained by the use of AIC (Akaike's Information Criterion) procedure is discussed under a loss function which is based on Kullback-Leibler information measure and evaluates both an error of model selection and that of estimation. Whenp is even, the minimaxity is shown to hold for small values ofp but not for large values.     

Synthesis of cytosinine,the nucleoside component of antibiotic blasticidin S

The first total synthesis of cytosinine (2) is described.     

Minimax estimation method for the optimum decomposition of a sample space based on prior information

Summary Existences and expressions of minimax estimators based on prior information for the optimum decomposition of a given sample space are studied in a unifying way such that answers can be easily obtained by applying the theorems given in this paper to various statistical problems—optimum selection regions, tolerance regions, prediction regions, optimum stratifications and so on. Further, ε-approximations to those estimators are given by choosing a finite family of probability measures from the infinite family of them under consideration in such a way that the former may be considered to be a sufficiently good approximation to the latter in the sense of risk function. Besides, those estimators are proved to be consistent in the sense that the risk decreases to zero as the amount of prior information increases infinitely. The Institute of Statistical mathematics     

Flexible Enantiodivergent Synthesis and Biological Activity of Mannostatin Analogues, New Cyclitol Glycosidase Inhibitors

Mannostatin A (1) is a new cyclitol inhibitor of glycoprotein processing. 2-Epimannostatin A (12) and its enantiomer (13) as well as their positional isomers (14, 15) were designed for probing structure-activity relationships in this class of glycosidase inhibitors. The analogues have been synthesized from (S)-4-((tert-butyldimethylsilyl)oxy)-2-cyclopentenone by an enantiodivergent strategy in a totally stereospecific fashion. Compound 13 showed inhibition against almond beta-glucosidase and is shown to be a topographical analogue of beta-D-glucopyranoside.     

Potassium-thiacalix[8]arene assembly: structure and guest sorption profiles

Treatment of thiacalix[8]arene (3.8H) with KH in THF, followed by recrystallization from methanol, affords an adduct of [K4(3.4H)].8MeOH as a pale yellow crystal (4), which shows highly-extensive coordination that gives rise to a zeolitic structure. An adduct of 4 gives apohost [K4(3.4H)] with the loss of methanol, which can adsorb such gaseous organic guest molecules as methanol and benzene. After binding methanol as the guest molecule, the apohost is converted back to the original structure of 4.     

Carbonylation reaction of aryl halides on a polymer support using in situ-generated carbon monoxide without the assistance of microwaves

Palladium-catalyzed carbonylation, which was based on a ligand exchange reaction, efficiently converted immobilized aryl halides to amides under mild reaction conditions using molybdenum hexacarbonyl [Mo(CO)(6)] as the carbon monoxide source. The method easily operates without irradiating with microwaves and yields a wide range of highly pure amides after cleaving from the resin. The method could also be applied to the carbonylation of immobilized amines with aryl halides and to construct heterocyclic systems via a carbonylative cyclization.