Structure of the liquid crystalline state in hexakis (4-(4'-alkyloxy)biphenoxy)cyclotriphosphazenes

X-ray measurements on hexakis(4-(4'-alkyloxy)biphenoxy)cyclotriphosphazenes [PN-(OC₆H₄C₆H₄OC_nH_{2n + 1})₂]₃ (HACP, n = 7-9), confirm the previous mesophase identification. The apparent molecular length measured in the mesophase compares to twice the length of an alkyloxybiphenyl side group. Specific features are added to the usual features of the nematic and smectic diffraction patterns which show that the molecular arrays in directions parallel and perpendicular to the director both reflect the peculiar shape of the cyclotriphosphazenes.     

Total synthesis of (+)- and (-)-sundiversifolide via intramolecular acylation and determination of the absolute configuration

Intramolecular acylation of an organolithium leads to an efficient stereocontrolled total synthesis of both enantiomers of sundiversifolide. The absolute configuration was determined by HPLC analysis and allelopathy assay. The gamma-lactone moiety resulted from a butenolide was obtained by the condensation of a bicyclic alpha-hydroxyhemiacetal with Ph3P=CMe(CO2R).     

Stereoselective Retentive Domino Transmetalations of Secondary Alkyllithium Compounds to Functionalized Secondary Alkylcopper Reagents

Functionalized secondary alkyllithium reagents obtained by I/Li exchange from the corresponding secondary alkyl iodides undergo two successive transmetalations with Me₃SiCH₂ZnBr?LiBr and CuBr?2 LiCl?Me₂S to provide functionalized secondary alkylcopper compounds with high retention of configuration. These alkylcopper derivatives react further with electrophiles such as alkynyl esters, acid chlorides, allylic chlorides, ketals, ethylene oxide, and 3‐iodocyclopentanone with high retention of configuration. A related sequence of transmetalations with MeMgI and LaCl₃?2 LiCl allows a retentive addition of secondary alkyllithium reagents to acetone. The influence of the solvent on the configurational stability of secondary alkylzinc reagents is described.     

Single-step thioetherification by indium-catalyzed reductive coupling of carboxylic acids with thiols

Direct thioetherification from a variety of aromatic carboxylic acids and thiols using a reducing system combined with InBr(3) and 1,1,3,3-teramethyldisiloxane (TMDS) in a one-pot procedure is demonstrated. It was also found that a system combined with InI(3) and TMDS underwent thioetherification of aliphatic carboxylic acids with thiols.     

New upper bounds for the Davenport and for the Erdős–Ginzburg–Ziv constants

Let G be a finite abelian group (written additively) of rank r with invariants n ₁, n ₂, . . . , n _r , where n _r is the exponent of G. In this paper, we prove an upper bound for the Davenport constant D(G) of G as follows; D(G) ≤ n _r + n _r-1 + (c(3) − 1)n _r-2 + (c(4) − 1) n _r-3 + · · · + (c(r) − 1)n ₁ + 1, where c(i) is the Alon–Dubiner constant, which depends only on the rank of the group \mathbb Z_nrⁱ{{\mathbb Z}_{n_r}^i}. Also, we shall give an application of Davenport’s constant to smooth numbers related to the Quadratic sieve.     

Luminescence-based colorimetric discrimination of single-nucleotide transversions by the combined use of the derivatives of DOTA-conjugated naphthyridine and its terbium complex

We newly synthesized a nucleobase-binding ligand, ND-DOTA, in which 2-amino-5,7-dimethyl-1,8-naphthyridine (ND) was conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DOTA) via an amide linker, and found that its terbium(III) complex (ND-DOTA-Tb) showed green emission based on an energy transfer from the naphthyridine moiety to Tb³⁺. The blue emission of ND-DOTA was selectively quenched by adding abasic site-containing DNA duplexes that have pyrimidine bases opposite to the abasic site. In contrast, at the same excitation wavelength, ND-DOTA-Tb showed green emission independently of the bases opposite to the abasic site. Thus, a mixed solution of ND-DOTA and ND-DOTA-Tb enabled the luminescence-based colorimetric discrimination of single-nucleotide transversions with the naked eye at a single excitation wavelength.