Practical Enantioselective Arylation and Heteroarylation of Aldehydes with In Situ Prepared Organotitanium Reagents Catalyzed by 3‐Aryl‐H8‐BINOL‐Derived Titanium Complexes

A highly efficient and practical method for the catalytic enantioselective arylation and heteroarylation of aldehydes with organotitanium reagents, prepared in situ by the reaction of aryl‐ and heteroaryllithium reagents with ClTi(OiPr)₃, is described. Titanium complexes derived from DPP‐H₈‐BINOL ( 3 d ; DPP=3,5‐diphenylphenyl) and DTBP‐H₈‐BINOL ( 3 e ; DTBP=3,5‐di‐tert‐butylphenyl) exhibit excellent catalytic activity in terms of enantioselectivity and turnover efficiency for the transformation, providing diaryl‐, aryl heteroaryl‐, and diheteroarylmethanol derivatives in high enantioselectivity at low catalyst loading (0.2–2 mol %). The reaction begins with a variety of aryl and heteroaryl bromides through their conversion into organolithium intermediates by Br/Li exchange with nBuLi, thus providing straightforward access to a range of enantioenriched alcohols from commercially available starting materials. Various 2‐thienylmethanols can be synthesized enantioselectively by using commercially available 2‐thienyllithium in THF. The reaction can be carried out on a 10 mmol scale at 0.5 mol % catalyst loading, demonstrating its preparative utility.     

Synthesis of 10‐Aryl‐ and 10‐(Arylmethyl)acridin‐9(10H)‐ones via the Reaction of (2‐Fluorophenyl)(2‐halophenyl)methanones with Benzenamines and Arylmethanamines

The reaction of 1‐fluoro‐2‐lithiobenzenes, generated from 1‐bromo‐2‐fluorobenzenes 1 and BuLi, with 2‐halobenzaldehydes and subsequent oxidation of the resulting alcohols 2 afforded (2‐fluorophenyl)(2‐halophenyl)methanones 3 , which, on treatment with benzenamines or arylmethanamines, followed by NaH, gave rise efficiently to 10‐aryl‐ or 10‐(arylmethyl)acridin‐9(10H)‐ones ( 5 or 7 ), respectively.     

Synthesis and Properties of Carbocyclic 5′- Nor Oligodeoxynucleotides as Potential Antisense Molecules

We have synthesized carbocyclic 5'-nor oligodeoxynucleotides with a shortened overall chain length lacking the 5'-methylene. Their hybridization properties with DNA and RNA were investigated by UV and CD melting curves. These oligomers formed unstable duplexes with DNA, but formed stable duplexes with RNA selectively. In addition, these oligomers were very stable against nucleases.     

Separation of the molecular species of diacyl and alkenylacyl subclasses of the methyl ester of dinitrophenylethanolamine glycerophospholipid by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) procedure for the separation of the molecular species of alkenylacyl and diacyl subclasses after the derivatization of ethanolamine glycero-phospholipids (EGP) to the methyl ester of the dinitrophenylated lipids is described. Methyl esters of dinitrophenylethanolamine glycerophospholipids were first separated into alkenylacyl, alkylacyl and diacyl subclasses by thin-layer chromatography, then each subclass was separated into individual molecular species by reversed-phase HPLC. By converting the EGP into UV-absorbing derivatives, it proved possible to utilize the specificity of spectrophotometric detection for the determination of the individual molecular species. Alkenylacyl and diacyl derivatives were resolved into fifteen to twenty different species in a single HPLC run. The method should facilitate studies on the metabolism of the polar head group of both molecular species of alkenylacyl and diacyl glycerophosphoethanolamine in a variety of tissues using radioactive precursors.     

Synthesis of 5,10,15,20-tetrakis(4-tert- butyl-2,6-dicarboxyphenyl)porphyrin: a versatile bis-faced porphyrin synthon for D4-symmetric chiral porphyrins

[see structure]. A versatile bis-faced porphyrin synthon, 5,10,15,20-tetrakis(4-tert-butyl-2,6-dicarboxyphenyl)porphyrin, was synthesized. The eight carboxyl groups were readily converted into various amide groups, and condensation with chiral amines led to various D4-symmetric chiral porphyrins with rigid structures.     

On thermal convection between two coaxial square containers inclined by 45°

This paper is concerned with flow visualization, velocity, streakline, and heat transfer measurements on thermal convection between two coaxial square containers inclined by 45°. It is found that there is no critical Rayleigh number (Ra)_c for the onset of thermal convection in the test section. There appear two great circulations, which are symmetrical with respect to the diagonal vertical plane of the two coaxial square containers, and enhance the heat transfer significantly. Received on 23 October 1997     

Fission yeast living mitosis visualized by GFP-tagged gene products.

The fission yeast Schizosaccharomyces pombe has been used as a model organism to study cell cycle control and dynamic chromosome behavior during anaphase segregation as genetic and cytological approaches are easily amenable. To understand the role of gene products involved in these cellular events, it is important to determine intracellular localization of each gene product during the cell cycle. In this article, visualization in living cells of several gene products involved in cell cycle control and sister chromatid separation is described. The genes tagged with jellyfish green fluorescent protein (GFP) include sad1(+) (encoding a spindle pole body (SPB) protein), atb2(+) (alpha-tubulin), mis6(+) (a kinetochore protein), eat1(+) (a novel actin-like protein localized in the nucleus) and cdc13(+) (a mitotic cyclin). In addition, LacI which is bound to a DNA segment containing LacO repeat sequences integrated near the centromere (cen1) is visualized. These are useful to monitor cell cycle events in living cells.