Indole-3-propionic acid, oxidation

Beccalli et al. reported a new synthesis of staurosporinone (293) from 3-cyano-3-(lH-indol-3-yl)-2-oxo propionic acid ethyl ester (1464) (790). The reaction of 1464 with ethyl chlorocarbonate and triethylamine afforded the compound 1465, which, on treatment with dimethylamine, led to the corresponding hydroxy derivative 1466. The triflate 1467 was prepared from 1466 by reaction with trifluoromethanesulfonic anhydride (Tf20) in the presence of ethyldiisopropylamine. The palladium(O)-catalyzed cross-coupling of the triflate 1467 with the 3-(tributylstannyl)indole 1468 afforded the vinylindole 1469 in 89% yield. Deprotection of both nitrogen atoms with sodium ethoxide in ethanol to 1470, followed by photocyclization in the presence of iodine as the oxidizing agent provided the indolocarbazole 1471. Finally, reductive cyclization of 1471 with sodium borohydride-cobaltous chloride led to staurosporinone (293) in 40% yield (790) (Scheme 5.248). 

The reaction of nitroarenes with silyl end ethers and ketene silyl acetals in MeCNATiF with 1 equiv. of TASF, followed by in situ oxidation with Br2 or DDQ, provides an easy route to a-nitroaryl carbonyl compounds (Scheme l).12 The use of these compounds as reagents for the synthesis of arylacetic acids, propionic acids, indoles, 2-indolinones and other heterocyclic compounds has recently been described.88... 

Tryptophan-59 has been modified by formylation, with the formyl group replacing the NH proton on the indole ring, and oxidation with V-bromosuccinimide (NBS). In both cases the hydrogen bond to the buried heme propionic acid is broken, and the molecule undergoes the change in properties outlined in Table XV. Reductase activity is impaired, and the oxidase reaction is also affected somewhat The reaction is slower for any given cytochrome c concentration short of saturation, but the Vm x is the same as for unmodified cytochrome c. The NBS story... 

In agreement with the derived structure hexahydrodeazanorvobasine, upon oxidation with chromic acid, formed a-methylbutyric acid in addition to acetic and propionic acids. Also in complete harmony with the chosen structure was the formation of trideuterio-16-epivobasine by a base-catalyzed deuteration (MeOD/MeONa) of vobasine followed by reprotonation of the indole nitrogen. 

XLIII) the IR-spectrum of its iodide is also similar to that of sempervirine iodide and further shows the absence of a vinyl group. Catalytic hydrogenation of melinonine G over Adams catalyst in aqueous alkaline solution gives an indole which yields propionic and acetic acids on modified Kuhn-Roth oxidation and which, therefore, contains a C-ethyl group. All this evidence is accommodated in structure XLIV for melinonine G the indolic reduction product must then have structure... 

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