Norimasa Yamazaki

Highly reactive and stereospecific reaction of quinoline-type NADH model compounds with methyl benzoylformate

Abstract NADH model compounds with a dihydroquinoline ring can reduce methyl benzoylformate with very high reactivity and stereospecificity. Chiral column HPLC is effective in the separation and analysis of enantiomers of NADH and NAD model compounds, respectively.

Stereoselective C4 alkylation of NAD(P)+ analogs

Abstract Alkylation of NAD(P) + analogs with Grignard reagents gave C4-alkylated NAD(P)H analogs in high regio- and stereoselectivity.

NAD(P)+-NAD(P)H models. 90. Stereoselection controlled by electronic effect of a carbonyl group in oxidation of NAD(P)H analog.

4-Monodeuterated NAD(P)H model compounds (1,4,6,7-tetrahydro-1,6,11-trimethyl-5-oxo-5H-benzo[c]pyrido[2,3-e]az epin; 11Me-MMPAH) have been oxidized with a series of p-benzoquinone and its derivatives in the presence of Mg2+. The models have an axial chirality with respect to the orientation of carbonyl dipole, the dihedral angle of which is larger than 55 degrees out of the plane of dihydropyridine ring. Without Mg2+, the anti- (with respect to the carbonyl dipole) hydrogen is 3 to 32 times more reactive than the corresponding syn-hydrogen, whereas, when Mg2+ is present in the system, the selectivity is shifted toward the syn-preferency. Mg2+ plays the role of a Lewis acid catalyst to control the stereochemistry at the same time as it catalyzes the reaction.

Retention of configuration in ligand coupling reactions in σ-sulphuranes

In accord with the ligand coupling concept, an axial and an equatorial ligand are considered to be extruded from the valence-shell-expanded heteroatom in a concerted fashion which thus affords the coupling product. Therefore, the coupling ligands should retain the original configuration. Indeed, the ligand coupling product, p-(1 -Phenylethyl)phenylsulphonylbenzene (3) formed in the reaction of 1 -phenylethyl benzene-p-sulphonylphenyl sulphoxide (2) with ethylmagnesium bromide is found to retain completely the 1 -phenylethyl group configuration, as in our earlier example of the coupling reaction of optically active 1 -phenylethyl 2-pyridyl sulphoxide with Grignard reagents and that of allylic and vinylic sulphoxides with Grignard reagents. The absolute configuration of (+)-(2) and (+)-(3) are determined unequivocally to be SsRc and Rc, respectively, by X-ray methods.

NAD(P)+-NAD(P)H models. 89. Effect of magnesium ion on the stereochemistry in oxidation of NAD(P)H analog

Abstract In oxidation of NAD(P)H analog with p-benzoquinone derivatives in the presence of Mg 2+ , it has been found that the reactivity of syn-hydrogen becomes larger as the reduction potential of p -benzoquinone derivative decreases. The selectivity shifts toward the syn-preferency in the presence of Mg 2+ from the anti -preferency in the absence of Mg 2+ .

Synthesis and characterization of 10-Se-3 type selenatetraazapentalene derivatives with a hypervalent selenium

Abstract Symmetrical 12π-selenatetraazapentalene derivatives 3–5 were synthesized by a convenient one-pot reaction using the lithium selenoureide/phenacyl chloride/alkyl (or allyl) isothiocyanate system. The structure was determined by a single crystal X-ray diffraction of 4. The reactions of 3 and 5 with alkyl iodides and ω-bromoalkyl isothiocyanates gave the novel selenatetraazapentalene derivatives.

STEREOSPECIFIC REDOX REACTION DIRECTED BY A SULFINYL GROUP

Stereochemistry of reductions of a pyridinium and quinoliniums with an asymmetric sulfinyl group has been studied. Dithionite and borohydride prefer the face characterized by a lone pair on sulfur atom. Dihydropyridine prefers the face characterized by a S-O bond.