14-hydroxy methine

The compound crystallized from methanol and showed a typical N-acylindoline UV spectrum. The IR spectrum indicated both hydroxyl (3610 cm-1) and tertiary amide (1670 cm-1) functionalities, and the PMR spectrum showed a hydroxy methine proton at 4.45 ppm and two signgfe for the formyl proton at 8.41 and 8.87 ppm, totaling one proton. 

The methylenedioxy substituted isopavine amurensine was prepared by a parallel method, as were the related bases reframine and reframoline. In the latter study, undertaken to confirm the structure of reframoline, the two positional isomers with respect to the hydroxyl and methoxyl groups, namely, 5 and 6, were prepared synthetically, but could not be distinguished by spectral means. They were, however, easily characterized by way of the UV spectra of their respective methine bases, 7 and 8. The 3-hydroxy methine base exhibited a large bathochromic shift upon the addition of base, while little alteration of the spectrum of the 2-hydroxy isomer occurred in base ... 

In comparison with mercapto-, hydroxy-, and amino-pyridines, methylpyridines should show an even greater tendency to exist in the methyl form [instead of as pyridmethines (297)] than do the amino compounds to exist as such. If the methyl carbon atom carries an electron-withdrawing group, it might be expected that structures of type 297 would be stabilized. Fused benzo groups should also tend to stabilize the methine form, and tautomerism involving 298 has, in-... 

Mesoionic thiazol-4-one, see 4-Hydroxy-thiazolium hydroxide inner salts Methanol, action on thiazolium salts, 32 Methine dyes, nonionic, nomenclature of, 27... 

CH3)2CDOH it is slowed by a factor of ca 5. This confirms that the primary reaction of 3BA with isopropyl alcohol is abstraction of the methine hydrogen to give BAH, which is observed spectroscopically, and the 2-hydroxy-2-propyl radical. These radicals combine and disproportionate to form the stable products. 

Chemical degradations have allowed the identification of both extremities of peripentadenine, hexanoic acid (present as an amide) and 2-hydroxy-6-meth-ylacetophenone. 13C NMR showed that the rest of the molecule included two nitrogen atoms, six methylenes, and one methine arranged in a (3-propylami-no)-l-pyrrolidine unit substituted at C-2. This formula was definitively proved by chemical degradations as well as by two total syntheses. As noted before in the cases of hygrine and of the ruspolinone alkaloids, peripentadenine is optically inactive. 

Quinophthalone (6.229) and its derivatives [86] also fall into the methine category, although they appear in the Colour Index under quinoline colouring matters. The parent compound was discovered in 1882 by Jacobsen, who condensed 2-methylquinoline (quinaldine) with phthalic anhydride. The product, quinoline yellow, is used as a solvent dye (Cl Solvent Yellow 33). The light fastness is improved by the presence of a hydroxy group in the quinoline ring system. Derivatives of this type provide greenish yellow disperse dyes for polyester. The moderate sublimation fastness of Cl Disperse Yellow 54 (6.230 R = H) is improved by the introduction of an adjacent bromine atom in Cl Disperse Yellow 64 (6.230 R = Br). 

As an example, Figure 5.1.6 shows a 2D WET-TOCSY spectrum of ruberoside A. In this figure, a correlation between a downfield methine proton at 3.67 ppm and both the aglycone methyl groups A-H3-26/27 (0.84/0.86 ppm) and A-H3-2I (0.90 ppm) confirms the 23-hydroxy function in the side-chain which was suggested by the on-flow NMR and MS-back-exchange data (see above). Ruberoside A was thus identified as a new asterosaponin and subjected to semipreparative isolation. 

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