Entire genomes of hepatitis B virus (subtype adr) have been cloned. The nucleotide sequence data were compared with other sequences of HBV genome including: adw [Valenzuela et al. (1981) in Animal Virus Genetics. Fields et al. eds. Academic Press, Inc., NY. pp. 57-70], ayw [Galibert et al. (1979) Nature, 281, 646-650], and adyw [Pasek et al. (1979) Nature 282, 575-579]. Four open coding frames for polypeptides larger than 6,000 dalton were found to be conserved and were highly compressed by overlapping with each other in one strand (L-strand). Sites of initiation of the S gene and termination of the P gene were not conserved. No conserved coding frame was found on the opposite strand (S strand). Amino acid sequences of six surface antigen (HBsAg) peptides, including subtypes adr, adw, and ayw, are deduced from the DNA sequences, and the substitution of amino acid residues which are consistent with the change of subtypes are demonstrated.

Substitution of phosphine ligands in nickel(II) halide complexes by now attractive N-heterocyclic carbene (NHC) ligands is one of the well-known organometallic reactions. New, simple, and easy-to-prepare nickel(II) halides bearing both a phosphine and an NHC ligand, [NiX2(PPh3)(NHC)], were synthesized by the reaction of [NiX2(PPh3)2] (X = Cl and Br) with 1 equiv of a bulky NHC ligand. Rather small NHC ligands did not form NHC/PR3 mixed complexes. Controlling the amount of the NHC ligand and purification led to successful isolation in good to moderate yields and structural determination of these carbene complexes. Studies on catalytic Grignard cross-coupling reactions using three complexes, the NHC/PPh3 mixed complex, a “bis”-carbene complex, and [NiCl2(PPh3)2], revealed that the monocarbene complex catalyzes reactions with the highest activity, but, in comparison, catalysis does not proceed well using the latter two complexes.

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Novel T-shape three-coordinate nickel(I) chlorides bearing an N-heterocyclic carbene ligand, NiCl(IPr)(2) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene), were isolated by a reaction of Ni(0)(NHC)(2) with aryl chlorides. This Ni(I) complex was shown to act as a catalyst in a cross-coupling reaction of aryl halides with phenylmagnesium chloride.

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Highly active dinuclear nickel(I) complexes bearing bulky N-heterocyclic carbene ligands have been shown to be involved in the catalytic cycle of the Kumada−Tamao− Corriu cross-coupling reaction of aryl halides. The results of several stoichiometric reactions and kinetics experiments have revealed that monovalent and divalent dinickel species are the active species in the highly efficient, nickel-catalyzed, Kumada coupling reactions of aryl halides.

An efficient reduction of carboxylic acids, esters, and amides with trialkylsilanes is accomplished using a triruthenium carbonyl cluster bearing a bridging acenaphthylene ligand, (mu(3),eta(2):eta(3):eta(5)-acenaphthylene)Ru(3)(CO)(7), as the catalyst. Preactivation of the catalyst by hydrosilanes accelerates the reactions. Sterically small trialkylsilanes are effective in these reactions. Reduction of carboxylic acids and amides efficiently produces the corresponding silyl ethers and amines, respectively. Reduction of esters gives a mixture of silyl and alkyl ethers, but can be controlled by changing the silanes and solvents.