Aryl Species Research Articles

A new class of C-nucleoside analogues. 1-(S)-aryl-1,4-dideoxy-1,4-imino-D-ribitols, transition state analogue inhibitors of nucleoside hydrolase

The first members of a new class of N-glycohydrolase transition state analogue inhibitors, 1,4-dideoxy-1,4-imino-1-(S)-phenyl-D-ribitol, 1, and 1,4-dideoxy-1,4-imino-1-(S)-(4-imidazolyl)-D-ribitol, 2, have been synthesized. These compounds represent a new type of C-nucleoside analogue in which the endocyclic ribosyl ring oxygen has been replaced with nitrogen. The key synthetic step involves reaction of a protected ribosylimine with a metallated aryl species. The compounds are transition state analogues for enzymes which catalyzed CN glycosidic bond hydrolyses of nucleosides and have transition states with oxocarbenium ion character. Compounds 1 and 2 are potent competitive inhibitors with dissociation constants of 0.03 and 2.5 μM, for nucleoside hydrolase from the trypanosome Crithidia fasciculata. The highly effective inhibition observed demonstrates the importance of including both charge and aglycon mimicry in a glycosylase transition state analogue and differentiates it from simpler analogues.

ChemInform Abstract: Syntheses and Characterization of Unique Organometallic Nickel(III) Aryl Species. ESR and Electrochemical Studies and the X‐Ray Molecular Study of Square‐Pyramidal (Ni(C6H3(CH2NMe2)2‐o,o′)I2).

AbstractThe oxidation of the Ni(II) species (I) and (IV) by CuX2 (II) or I2 (V) affords the air‐stable, square‐pyramidal Ni(III) aryl species (IIIa) and (IIIb) that are precursors to the NO2 and NO3 analogues (IIIc).

Syntheses and characterization of unique organometallic nickel(III) aryl species. ESR and electrochemical studies and the x-ray molecular study of square-pyramidal [Ni{C6H3(CH2NMe2)2-o,o'}I2

Syntheses and characterization of unique organometallic nickel(III) aryl species. ESR and electrochemical studies and the x-ray molecular study of square-pyramidal [Ni{C6H3(CH2NMe2)2-o,o'}I2

Reactive silica: XVI. Reaction with cyclopropane, benzene, and toluene

Infrared spectroscopy was used to follow the sorptions of relatively stable adsorbates by reactive silica. Dissociative chemisorption occurred in each case. With cyclopropane, the ring was disrupted and at least three distinct surface species were formed. The main surface product resulting from cyclopropane sorption was also formed when propene was adsorbed. Ring disruption also occurred with benzene, leading to the formation of silanols and some coke-like hydrocarbons, but surface aryls were not observed. However, two surface aryl species were formed with toluene.

Photochemical investigations of some DI-η 5-cyclopentadienyldiaryltitanium compounds

The photolysis of (η 5-C 5H 5)Ti(C 6H 5) 2 in benzene solution leads to black titanocene and biphenyl. Studies in benzene- d 6 have shown that biphenyl- d 0 and biphenyl- d 5 are produced in ca. equal amounts. Photolysis of (η 5-C 5H 5) 2Ti( p-CH 3C 6H 4) 2 produces black titanocene, toluene, 4-methylbiphenyl and 4,4′-dimenthylbiphenyl, while photolysis of (η 5-C 5H 5) 2Ti( m-CH 3C 6H 4) 2 gives titanocene toluene, 3-methylbiphenyl and 3,3′-dimethylbiphenyl. The above results indicate that the biaryls are formed both by a reductive-elimination process as well as by attack of a radical-like aryl species on the solvent, and not by an ortho-phenylene or benzyne-type titanocene intermediate as has been suggested for the thermal decomposition of diaryltitanocenes. Photolysis of (η 5-C 5H 5) 2Ti(C 6H 5) 2 in the presence of either CO or PhCCPh leads to moderate yields of dicarbonyltitanocene and 1,1-di-η 5 cyclopentadienyl-2,3,4,5-tetraphenyltitanole, respectively.The formation of cis- and trans-stilbenes as well as cis,cis-1,2,3,4-tetraphenyl-1,3-butadiene in the latter reaction is indicative of titanium-hydride intermediates being formed under these photolytic conditions.