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H Rapoport

Publications and source records attributed to H Rapoport.

At least 55 records · Page 3Linked to original sources
PubMed1977

Stereochemistry of the porphyrin-protein bond of cytochrome c. Stereochemical comparison of Rhodospirillum rubrum, yeast, and horse heart porphyrins c.

Porphyrins c have been obtained from Rhodospirillum rubrum cytochrome c2, yeast cytochrome c, and horse heart cytochrome c and compared using proton magnetic resonance and circular dichroism. Identity of the spectra establishes that chemically and stereochemically the three porphyrins c are identical. Since the stereochemistry of the porphyrin alpha-thioether linkage is not affected in the conversion to porphyrin c, the stereochemistry at the porphyrin alpha-thioether bonds among the corresponding cytochromes c also must be the same. Differences between the proton magnetic resonance of R. rubrum cytochrome c2 and horse heart cytochrome c which were rationalized by invoking an opposite stereochemistry at these condensation sites (Smith, G. M., and Kamen, M. D. (1974), Proc. Natl. Acad. Sci. U.S.A. 71, 4303) must therefore be attributed to other factors.

Animals↗
PubMed1977

Synthesis and characterization of new psoralen derivatives with superior photoreactivity with DNA and RNA.

The synthesis of five new psoralen derivatives is described. Three of these, 4'-hydroxymethyl-4,5',8-trimethylpsoralen, 4'-methoxymethyl-4,5',8-trimethylpsoralen, and 4'-aminomethyl-4,5',8-trimethylpsoralen hydrochloride, and characterized with respect to their photoreactivity with DNA and RNA. They are found to be greatly superior to 4,5',8-trimethylpsoralen and 8-methoxypsoralen, the two commonly used psoralens, in their abilities to saturate the photoreactive sites on DNA and RNA without repeated addition of reagent. A simplified mechanism for the photoreaction of psoralens with nucleic acids is presented and provides a basis for understanding the superior properties of these compounds. The compounds have superior reactivity not only with isolated DNA and RNA but also in viruses and in cells. Psoralens are shown for the first time to cross-link RNA double helices.

Binding Sites↗
PubMed1976

A practical synthesis of codeine from dihydrothebainone.

The conversion of dihydrothebainone to codeine or thebaine has been achieved in high yield. Bromination and dehydrobromination constructs the 4,5-oxide bridge to give 1-bromo- and 1,7-dibromodihydrocodeinone which yield dihydrocodeinone practically quantitatively after catalytic debromination. Ketalization and acid-catalyzed elimination of methanol give excellent yields of delta6-dihydrothebaine to which is added methyl hypobromite using N-bromoacetamide in methanol. The action of potassium tert-butoxide in Me2SO on the resulting 7-bromodihydrocodeinone dimethyl ketal gives codeinone dimethyl ketal selectivity at 60 degrees while at 120 degrees thebaine is the exclusive product. Hydrolysis to codeinone and borohydride reduction give codeine in 70% overall yield. The bromo intermediates in the formation of the 4,5-oxide bridge have been examined. 1,5beta, 7alpha-Tribromodihydrothebainone has been identified as the main product in the tribromination of dihydrothebainone.

Codeine↗
PubMed1976

Conversion of Thebaine to Codeine.

An improved conversion of thebaine to codeine has been developed. Oxymercuration of thebaine with mercuric acetate in refluxing methanol, followed by hydrolysis of the intermediate 7-acetomercurineopinone dimethyl ketal with 3 N acetic acid, or, alternatively, reduction of the organomercury compound with sodium borohydride and mild acid hydrolysis of the resulting neopinone dimethyl ketal, gives neopinone in 95-100% yields. Either acid- or alkali-catalyzed isomerization to codeinone leads to the equilibrium mixture consisting of codeinone-neopinone, 3:1. Complete conversion to codeinone in 85-90% yield results from treatment of neopinone with anhydrous hydrogen chloride or hydrogen bromide in ether-methylene chloride, followed by elimination of hydrogen halide from the intermediate 8-halodihydrocodeinone. The known borohydride reduction of codeinone then gives codeine in 85% overall yield from thebaine.

Codeine↗
PubMed1975

Synthesis of thebaine and oripavine from codeine and morphine.

A practical synthesis of thebaine and oripavine has been developed from codeine and morphine, respectively. Attempts to use a codeinone intermediate gave poor yields; however, methylation of the potassium salt of codeine to give codeine methyl ether followed by oxidation with gamma-MnO2 gave thebaine in 67% yield from codeine. Similarly, the potassium salt of the di-O-anion of morphine was selectively alkylated to give morphine 6-methyl ether (heterocodeine) in better than 90% yield. Hetercodeine was then acetylated and oxidized to oripavine 3-acetate which was hydrolyzed to give oripavine in 73% yield from morphine.

Codeine↗