Molecular Structure of 3-Hydroxy-4-Pyrone

Abstract

Aerial parts of Erigeron annuus and E. strigosus afforded 3-hydroxy-4-pyrone, the molecular structure of which was determined by single crystal X-ray diffraction.     

Synthesis of oligonucleotides containing thiazole and thiazole N-oxide nucleobases

[reaction: see text] The thiazole C-nucleoside analogue was synthesized by the Hantzsch cyclization method to form the thiazole ring and was then converted to the thiazole N-oxide C-nucleoside analogue by peracid oxidation of the heterocycle nitrogen. Incorporation of the thiazole and thiazole N-oxide phosphoramidites into DNA was successful though significant deoxygenation of the N-oxide occurred during DNA assembly. The mechanism proposed for the reduction of the thiazole N-oxide to thiazole involves the formation of an N-oxide phosphite ester.     

A new cryptand: synthesis and complexation with paraquat

[formula: see text] Inspired by folded, nonpseudorotaxane complexes of bis(m-phenylene)-32-crown-10 systems, we synthesized a new bicyclic crown ether containing two 1,3,5-phenylene units linked by three tetra(ethyleneoxy) units. The new cryptand forms a "pseudorotaxane-like" inclusion complex with N,N'-dimethyl-4,4'-bipyridinium bis(hexafluorophosphate) with association constant Ka = 6.1 x 10(4) M-1, 100-fold greater than that of an analogous simple crown ether.     

Synthesis of a reaction intermediate analogue of biotin-dependent carboxylases via a selective derivatization of biotin

[formula: see text] An efficient and practical synthesis of 1, a unique reaction intermediate analogue of biotin-dependent carboxylases, is described. The synthesis features a selective acylation of the 1'-N of biotin. Target 1 inhibits the activity of the biotin carboxylase component of acetyl CoA carboxylase. It is the first known biotin-derived inhibitor of biotin carboxylase and should promote new kinetic and structural studies of the biotin-dependent carboxylases.     

Crystal structure and luminescence of 2,7-dimethylnaphthalene-1-carbonitrile

The title compound crystallizes in the monoclinic space group P2 ₁/c: M _r = 181.2; a = 7.119(1), b = 18.389(4), c = 7.5385(6) Å = 91.661(7)° V = 986.4(5) ų; and Z = 4. The purified material shows fluorescence similar to other naphthalene derivatives: monomer fluorescence (_max 350-370 nm) in the solid state and in dilute solutions, and excimer fluorescence (_max 421 nm) in concentrated solutions. Intense blue-green luminescence (_max 490 nm) is observed in some partially purified crystalline samples. This is attributed to phosphorescence from two isomeric bromodimethylnaphthalenecarbonitrile impurities detected by GC-MS analysis.     

The crystal and molecular structure of 3,3,6,6-tetramethyl-s-tetrathiane, ((CH3)2CS2]2,

The X-ray crystal structure of 3,3,6,6-tetramethyl-s-tetrathiane (“duplodithioacetone”) confirms earlier nmr studies predicting the molecule to adopt a twist-boat conformation.