Asymmetric total syntheses of two phlegmarine-type alkaloids, lycoposerramines-V and -W, newly isolated from Lycopodium serratum

Two new Phlegmarine-type alkaloids, lycoposerramines-V and -W, were isolated from Lycopodium serratum, and their structures including the absolute configuration were established by asymmetric total synthesis involving such key steps as Johnson-Claisen rearrangement, asymmetric allylation, and ring-closing metathesis (RCM)- or SmI(2)-mediated stereoselective piperidine ring construction.     

Synthesis of the common left-half part of pectenotoxins

The common left-half [C31-C33(OC1-C7)-C40] part of pectenotoxins has been synthesized convergently from the C31-C35, C36-C40, and C1-C7 parts. The C31-C35 part, prepared via a new route shorter than our previous route, was coupled with the C36-C40 part through reductive lithiation and addition reactions to give an adduct stereoselectively, which was converted to a cyclic acetal corresponding to the C31-C40 part. The left-half was synthesized by a three-step process including esterification of the C31-C40 part with the C1-C7 part.     

A remark on the definitions of viscosity solutions for the integro-differential equations with Lévy operators

We prove the equivalence of the three different definitions of the viscosity solution for the integro-differential equation with the Lévy operator. The two of the definitions are known in the preceding works of the author and the others, and the last one is new. A construction of a sequence of the approximating test functions to the subsolution (or the supersolution) is indispensable for the proof, and it is done explicitly in the paper.     

Nickel-catalyzed multi-component coupling reaction of aldimine, alkyne, and dimethylzinc via dimerization of butadiene

In the presence of a Ni/phosphine ligand catalyst, dimethylzinc, alkyne, butadiene, aldehyde, and primary amine were successively combined via dimerization of butadiene to provide (3E,7E,10Z)-dodecatrienylamine in good yields with excellent regio and stereoselectivities.     

Synthesis of a secretoglobin 3A2 type C (98–139) fragment by Dawson’s native chemical ligation

A secretoglobin 3A2 type C (98–139) peptide was synthesized by native chemical ligation between ¹¹⁵Ile and ¹¹⁶Cys residues using Dawson’s linker. The peptide-N-acyl-benzimidazolinone-glycine amide, a C-terminal thioesters precursor, was provided from 3-amino-4-(methylamino)benzoic acid. In addition, an N-terminal cysteine fragment, the (116–139) peptide, was prepared by ordinary Fmoc-solid phase peptide synthesis. Native chemical ligation of the (98–115) fragment with the Dawson’s linker and the (116–139) peptide smoothly proceeded to give SCGB3A2 type C (98–139) peptide.     

A construction of rational elliptic surfaces with the non-surjective boundary map on K 2

We present some rational elliptic surfaces over a certain field such that certain open subschemes do not satisfy the surjectivity of the boundary map on K ₂ arising from the localization sequence. We consider two cases that the base field is transcendental over its prime subfield and that the base field is characteristic zero.     

Chemical synthesis and application of C-terminally 5-carboxyfluorescein-labelled thymopentin as a fluorescent probe for thymopoietin receptor.

Thymopentin (TP5) is a synthetic pentapeptide fragment, which corresponds to position 32 - 36 of thymic polypeptide thymopoietin. Thymopoietin and TP5 display a variety of biological functions, including phenotypic differentiation of T cells and the regulation of immune systems. Previous chemical modification experiments suggested that there was an absolute requirement for N-terminal amino acids to maintain the biological activity of TP5. On the basis of this structure-activity relationship, we designed and synthesized the C-terminally 5-carboxyfluorescein-coupled TP5 (TP5-FAM) as a fluorescent probe for thymopoietin receptor. TP5-FAM could bind to the membrane of human lymphoid cell lines, MOLT-4 cells, in which the thymopoietin receptor is expressed. The binding is specific and saturable (K(d) = 33 microM). TP5 and human splenopentin are nearly equipotent inhibitors of TP5-FAM binding to the thymopoietin receptor, but porcine secretin did not show any significant inhibition of TP5-FAM binding to MOLT-4 cells. Thus, TP5-FAM is suggested to be a potent and biologically active ligand that would be useful for studying the binding and functional characteristics of the human thymopoietin receptor.     

Scheme and studies of reference materials for volumetric analysis in Japan

This paper describes the history and scheme of reference materials and standard solutions for titrimetry in Japan. Titrimetry is one of the most fundamental and precise methods for determination of a constituent, based on the effective purity of reference materials in stoichiometric analysis. It has wide-ranging applications based on titrimetric reactions such as neutralization, redox, chelatometric, and precipitation titration processes, which are used in various analytical fields all over the world. Japanese Industrial Standards (JIS) have played an important role in establishing a stable supply of reference materials for titrimetry since the 1950s. There are several reports of preparations and their determination, including coulometric studies, in order to establish highly reliable reference materials. This paper briefly reviews the schemes and studies of standardization through the provision of reference materials and standard solutions based on JIS, and several applications in other standards. Presented at Berm-11, October 2007, Tsukuba, Japan.     

More analysis of double hashing

In [8], a deep and elegant analysis shows that double hashing is asymptotically equivalent to the ideal uniform hashing up to a load factor of about 0.319. In this paper we show how a randomization technique can be used to develop a surprisingly simple proof of the result that this equivalence holds for load factors arbitrarily close to 1.An earlier version of the paper was presented at the20th Annual ACM Symposium on Theory of Computing, Chicago, IL, May 1988.Supported by National Science Foundation Grants DCR 85-09667 and CCR 89-12063 at the University of California at IrvinePartially supported by National Science Foundation Grant DCR 85-09667 at the University of California at Irvine