Nitrosation of Phenolic Substrates under Mildly Basic Conditions: Selective Preparation of p-Quinone Monooximes and Their Antiviral Activities

Nitrosation of 3-methoxyphenol and 1-naphthol were examined under both acidic (NaNO(2)-EtCO(2)H-H(2)O) and basic (i-AmNO(2)-K(2)CO(3)-DMF) conditions. Acidic nitrosations afforded ortho-directed products, whereas para-directed nitrosations were observed under basic conditions to yield p-quinone monooximes. The basic para-directed nitrosation was further examined using 15 phenols, two naphthols, and four phenolic heterocyclics. A one-pot operation of the basic nitrosation followed by methylation with dimethyl sulfate gave the corresponding methyl ethers in high yield. Two p-quinone monooximes derived from 3-methoxyphenol and 8-hydroxyquinoline showed a moderate activity against HSV-1, and the latter oxime was also effective against HSV-2. On the other hand, p-quinone monooximes derived from methyl salicylate, 1-naphthol, 7-hydroxy-2-methylbenzo[b]furan, and 8-hydroxycoumarin showed the comparable activity to that of DDI against HIV-1.     

Alternating Sign Matrices and Some Deformations of Weyl's Denominator Formulas

An alternating sign matrix is a square matrix whose entries are 1, 0, or –1, and which satisfies certain conditions. Permutation matrices are alternating sign matrices. In this paper, we use the (generalized) Littlewood's formulas to expand the products and 2 as sums indexed by sets of alternating sign matrices invariant under a 180° rotation. If we put t = 1, these expansion formulas reduce to the Weyl's denominator formulas for the root systems of type B _n and C _n. A similar deformation of the denominator formula for type D _n is also given.     

Evaluation of dissociation constants of ammonium ion in aqueous lithium perchlorate and lithium chloride-sodium chloride mixed solutions

The Pitzer approach has been applied to the evaluation of dissociation constants of ammonium ion in lithium perchlorate and lithium chloride-sodium chloride mixed solutions at 25°C. The calculated values showed good agreement with the observed values, provided all the higher-order interaction terms ('s and 's) concerned were introduced. The unknown (NH₄LiClO₄) value was determined from the isopiestic measurements of NH₄ClO₄–LiClO₄ mixed solutions. Parameters in the Pitzer formalism for ammonia-ion interactions involved in LiCl and NaCl media were determined by use of the activity coefficients of ammonia measured in LiCl–NaCl mixed solutions by a transpiration method.     

Pi-face-selective Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide and 1-imide and formation of 1,2-thiazetidines

3,4-Di-tert-butylthiophene 1-oxide (1a) reacted with a series of electron-deficient alkenic dienophiles at its syn-pi-face relating to the S=O bond to give [4+2] adducts in excellent yields. The 1-oxide 1a also reacted even with angle-strained dienophiles acenaphthylene and norbornene at its syn-pi-face to afford [4+2] adducts; in the latter case, norbornene reacted exclusively at its exo-pi-face. The oxide 1a reacted with dimethyl acetylenedicarboxylate to produce dimethyl 4,5-di-tert-butylphthalate in high yield with spontaneous extrusion of SO from the initial adduct even at room temperature. Similarly, 3,4-di-tert-butylthiophene 1-(p-toluenesulfonyl)imide (3a) reacted with alkenic dienophiles at its syn-pi-face relating to the S=N bond to give [4+2] adducts in good yields. The reaction of 3a with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) afforded a 1,2-thiazetidine 12a, the first example of S-unoxidized 1,2-thiazetidine, in good yield, through rearrangement of the initial [4+2] adduct. The molecular structure of 12a is discussed on the basis of the X-ray crystallographic analysis. Comparison of the foregoing reactions leads to the conclusion that the 1-oxide 1a is more reactive as a diene than the 1-imide 3a, which is more reactive than 3,4-di-tert-butylthiophene 1,1-dioxide. The origin of the syn-pi-face selectivities of 1a and 3a in Diels-Alder reactions is discussed in terms of the orbital mixing rule and steric effect and also based on B3LYP/6-31G(d) calculations.     

Making the liquid-phase catalytic hydrodechlorination of pce over Pd/C safer

Summary The hydrodechlorination of tetrachloroethylene in methanol (MeOH) over palladium catalysts on activated carbon (Pd/C) at 20°C and atmospheric pressure was rendered safer by using ethanol (EtOH), isopropanol (IPA) or water-alcohol mixtures as solvents. Adding water to MeOH was better than using EtOH or IPA since it resulted in a faster reaction and better stability of Pd/C, which could also be completely reactivated.     

Ultraweak Luminescence Generated by Sweet Potato and Fusarium oxysporum Interactions Associated with a Defense Response

Abstract— Ultraweak luminescence generated by sweet potato and nonpathogenic Fusarium oxysporum interactions associated with a defense response was detected by a photoncounting method using ultrahigh-sensitive photodetectors. The time-dependent intensity variation, the spectrum and the two-dimensional imaging of the ultraweak luminescence are indicative of the defense response of the sweet potato to F. oxysporum. The production of ipomeamarone as a phytoalexin means that F. oxysporum induced the defense response in the sweet potato.     

Isolation of xylose reductase gene ofPichia stipitis and its expression inSaccharomyces cerevisiae

Applied Biochemistry and Biotechnology - A NADPH/NADH-dependent xylose reductase gene was isolated from the xylose-assimilating yeast,Pichia stipitis. DNA sequence analysis showed that the gene...