Synthesis of fused polycyclic aromatics by palladium-catalyzed annulation of arynes using 2-halobiaryls

The Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides provides a very efficient, high yielding synthesis of polycyclic aromatic and heteroaromatic hydrocarbons. This process appears to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

A light-driven rotaxane molecular shuttle with dual fluorescence addresses

[reaction: see text] A molecular shuttle containing an alpha-CD macrocycle, an azobenzene unit, and two different fluorescent naphthalimide units was synthesized. The cis-trans photoisomerization of the azobenzene unit resulted in the motion of the CD macrocycle on the track. Because of the easy regulation and full reversibility of the fluorescence change of the two stopper units, the molecular shuttle could be used as a molecular storage medium or switch with all-optical inputs and outputs.     

Heteroallen-komplexe des molybdänocens

Reactions of the extremely labile molybdenocene olefin complexe Mo(η⁵-C₅H₅)₂[(Z)-C₆H₅CH=CHC₆H₅] with heteroallenes X=C=Y (X=C=Y = CS₂, (p-tolyl)NCN(p-tolyl), (C₆H₅)₂CCO) gives the corresponding heteroallene complexes of molybdenocene Mo(η⁵-C₅H₅)₂(X=C=Y) in high yields. Spectroscopic data clearly indicate a dihapto-coordination of the heteroallenes via the C=X bond (X = O, S, N).     

Studies on the determination of diacetyl guanfubase A concentration in rabbit plasma and pharmacokinetics

A gas chromatographic method for monitoring diacetyl guanfubase A in plasma is described. The procedure involved a single solvent extraction of drug from rabbit plasma into ethyl acetate with guanfubase A as an internal standard. The extract was analyzed subsequently on a gas chromatograph equipped with a hydrogen flame ionization detector. The recovery was 86.43% +/- 6.90% (+/- SD); the RSD of within-day and between-day was 2.81%-5.26% and 5.22%-8.24%, respectively; the regression line was linear over the concentration range of 25-200 micrograms/mL, the limit of detection was 10 micrograms/mL. No endogeneous interference was found in chromatograms of the biological samples. This method was applied to the pharmacokinetic study of diacetyl guanfubase A in rabbits.     

Independent generation of 5-(2'-deoxycytidinyl)methyl radical and the formation of a novel cross-link lesion between 5-methylcytosine and guanine

Reactive oxygen species (ROS) can damage DNA. Although a number of single nucleobase lesions induced by ROS have been structurally characterized, only a few intrastrand cross-link lesions have been identified and characterized, and all of them involve adjacent thymine and guanine or adenine. In mammalian cells, the cytosines at CpG sites are methylated. On the basis of the similar reactivity of 5-methylcytosine and thymine toward hydroxyl radical and the similar orientation of adjacent thymine guanine (TG) and 5-methylcytosine guanine (mCG) in B-DNA, we predict that the cross-link lesion, which was identified in TG and has a covalent bond formed between the 5-methyl carbon atom of T and the C8 carbon atom of G, should also form at mCG site. Here, we report for the first time the independent generation of 5-(2'-deoxycytidinyl)methyl radical, and our results demonstrate that this radical can give rise to the predicted novel intrastrand cross-link lesion in dinucleoside monophosphates d(mCG) and d(GmC). Furthermore, we show that the cross-link lesion can also form in d(mCG) from gamma irradiation under anaerobic conditions.     

Determination of total arsenic in serum and packed cellsof patients with renal insufficiency

In order to investigate the arsenic level in serum and packed cells of patients with renal insufficiency, total arsenic (As) concentrations were determined with hydride generation atomic absorption spectrometry (HGAAS) in serum (S) and packed cells (PC) of 31 non-dialyzed patients. The accuracy of the method was tested by the analysis of arsenic in 3 certified reference materials. Patients showed a three-fold increase of arsenic concentrations in serum and a two-fold increase of arsenic in packed cells compared with controls. Patients (n=10) with higher serum creatinine (>2.0 mg/dL), urea (>0.70 g/L) and urinary protein (mean+/-SD: 1.12+/-0.82 g/L) showed higher arsenic concentrations (5.8+/-3.3 microg/L in serum and 18.0+/-16.7 microg/kg in packed cells) compared with those with lower creatinine (<1.6 mg/dL), urea (<0.6 g/L) and urinary protein (mean+/-SD: 0.27+/-0.82 g/L) (n=16, serum arsenic 1.2+/-1.2 microg/L, packed cells arsenic 2.6+/-1.9 microg/kg). The significant differences (both p < 0.001) in S and PC-arsenic levels of patients in group I and II implies a relationship between the arsenic level and the degree of chronic renal insufficiency.     

Total synthesis of the antiallergic naphtho-alpha-pyrone tetraglucoside,cassiaside C(2), isolated from cassia seeds

Toralactone 9-O-beta-d-glucopyranosyl-(1-->6)-beta-d-glucopyranosyl-(1-->3)-beta-d-glucopyranosyl-(1-->6)-beta-d-glucopyranoside (1, cassiaside C(2)), isolated from Cassia obtusifolia L. and showing strong antiallergic activity, was concisely synthesized employing glycosyl trifluoroacetimidates as glycosylation agents. The unique naphtho-alpha-pyrone structure of toralactone (5) was constructed by condensation of orsellinate 8 with pyrone 9 in the presence of LDA as developed by Staunton and co-workers. The naphthol of toralactone showed minimal reactivity as an acceptor and was screened with various glycosyl donors. It is finally concluded that sacrifice of an excess amount of the trifluoroacetimidate or trichloroacetimidate donors (6f/6g, 6.0 equiv) in the presence of a catalytic amount of TMSOTf (0.05 and 0.3 equiv, respectively) afforded excellent yields of the coupling product, which was otherwise only a minor product under a variety of conditions examined.     

氮杂冠醚研究Ⅶ、双仲胺型氮杂冠醚对过渡金属离子的选择性萃取作用

合成了五种新型双仲胺型氦杂冠醚，研究了它们对过渡金属离子进行液—液萃取，并用原子吸收法测定其浓度。实验结果表明：这类冠醚对Ａｇ￣＋、Ｐｄ￣（２＋）、和Ｐｔ￣（４＋）等贵金属离子有较强的选择配位性能，对选择性分离这些金属离子有重要的意义。