97522-07-1Relevant articles and documents
Total Synthesis of 4,5-Didehydroguadiscine: A Potent Melanogenesis Inhibitor from the Brazilian Medicinal Herb, Hornschuchia obliqua
Tanabe, Genzoh,Sugano, Youta,Shirato, Miki,Sonoda, Naoki,Tsutsui, Nozomi,Morikawa, Toshio,Ninomiya, Kiyofumi,Yoshikawa, Masayuki,Muraoka, Osamu
, p. 1536 - 1542 (2015/08/03)
The first total synthesis of the 7,7-dimethylaporphinoid, 4,5-didehydroguadiscine (6), originally isolated from the stems and roots of Hornschuchia oblique (Annonaceae), was achieved by the condensation of homopiperonylamine (7) with an α,α-dimethylphenylacetic acid derivative (8) and subsequent Pschorr reaction of the resulting benzylisoquinoline intermediate (22). The reported 13C NMR data were partially revised on the basis of the analysis of HMBC spectra measured under different conditions. The melanogenesis inhibitory activity (IC50 = 4.7 μM) of 6 was 40 times stronger than that of arbutin (174 μM), which was used as reference standard. Furthermore, 6 was the most potent natural melanogenesis inhibitor within this class of compounds. (Chemical Equation Presented).
Nucleophilic Addition of Silyl Enol Ethers to Aromatic Nitro Compounds: Scope and Mechanism of Reaction
RajanBabu, T. V.,Reddy, G. S.,Fukunaga, Tadamichi
, p. 5473 - 5483 (2007/10/02)
In sharp contrast to alkali-metal enolates, silyl enol ethers and ketene silyl acetals add to aromatic nitro compounds in the presence of a fluoride ion source to give the intermediate dihydroaromatic nitronates, which can be observed by NMR.In situ oxidation of the intermediate with bromine or DDQ yields α-nitroaryl carbonyl compounds in moderate-to-high yields.The reaction is applicable to alkyl-, alkoxy-, and halogen-substituted nitrobenzenes as well as to heterocyclic and condensed nitroaromatic compounds.While substitution ortho to the nitro group predominates with sterically undemanding silyl reagents, para-substitution products are exclusively obtained with bulky reagents.However, by blocking the para position with an appropriate group such as chlorine, the addition can be directed to the ortho position.Halogen atoms of halogenated nitroaromatics and p-nitrocumenyl chloride are not displaced in the reaction, suggesting the absence of radical ion intermediates.Dihydroaromatic nitro derivatives ca be isolated in some cases, such as anthracene and naphthalene systems which are less prone to rearomatize.
