Kuhn-Roth oxidation

When [2-14C]phenylalanine was administered to Decodon plants about two-thirds of the activity of decodine and decinine was located at C-2. This carbon was isolated as the a-naphthylamide of acetic acid by the Kuhn-Roth oxidation of the -propyl derivative. 

O-methyl groups a modified Kuhn-Roth oxidation gave a mixture of acetic and a-methylbutyric acids. These results allowed the following partial structure to be proposed for echitamine chloride and base C (76) ... 

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... 

Hofmann degradation of desbase A gives three products (79)2 one produced by a methoxylating fission, to which structure LXXI is ascribed, and two produced by D-type fission, didesbase AD, mp 73° (LXXII) and didesbase AD, mp 113° (LXXIII). Both these bases give the same tetrahydro derivative, hence they differ only in the position of the double bond. That V-type fission has not occurred is clear from the Kuhn-Roth oxidation of the tetrahydro derivative, which still shows the presence of only one G -methyl. 

The structure of LXXXII was demonstrated by its conversion by zinc and acetic acid into tetrahydro-18,19-chanostrychnine (LXXXIII R = H), methylation of which gave LXXXIII (R = CH3), which gave one equivalent of acetic acid on Kuhn-Roth oxidation and which was found not to be identical with 21,22-dihydro XC (see Section II, D, 1). The amorphous bromocyanamide-I was not further investigated. 

The incorporation of [2-14C]pyruvate and [l-14C]acetate into sugars 17 and 18 was investigated.27 Oxidation of the methyl glycosides of sugar 17 with periodate yielded acetaldehyde from the 1-hydroxyethyl branch. The acetaldehyde (2,4-dinitrophenyl)hydrazone was further oxidized by Kuhn-Roth oxidation to acetic acid, which was degraded by the Schmidt reaction to methylamine and carbon dioxide. Periodate oxidation of the methyl glycosides of sugar 18 produced acetic acid from the C-acetyl branch. The acetic acid was isolated, and purified as 1-acetamidonaphthalene. 

The first report of the incorporation of radioactively labelled mevalonic acid into dendrobine (82) was by Yamazaki et al. (224). Sodium [2— CJmevalonate [( )-463 ] was administered to stems of D. nobile by the cotton-wick method. After 12 days, the plants were extracted and radioactive dendrobine (82) was isolated by column chromatography. The total incorporation was 0.012%. Subsequent Kuhn-Roth oxidation led to acetic acid that showed the expected activity assuming the biosynthesis pathway a leading to the picrotoxanes via a cadalene as precursor (Scheme 55, pathway c). 

Further biosynthetic studies by Cane et have shown that the conversion of farnesyl pyrophosphate (15) into nerolidyl pyrophosphate (16) proceeds by a net syn (suprafacial) process and that the subsequent cyclization to cyclonerodiol (17) occurs in a trans manner (Scheme 4). This careful piece of work was achieved by incorporation studies with doubly labelled nerolidol and mevalonate precursors and then by ascertaining the chirality of the acetate derived by Kuhn-Roth oxidation through enzymatic conversion (malate synthase/fumarase incubation) into labelled malate. In a subsequent series of experiments with labelled precursors, Cane et have confirmed that (i) only the C-7 hydroxy-group in cyclonerodiol is derived from water whereas the C-3 hydroxy-group is derived... 

Clearly the most elegant chemical synthesis of chiral acetate is the route reported by Townsend et al. (33). The method, outlined in Scheme 2, has the advantage that tritium is introduced at a late stage in the synthesis, and both of the remaining steps, pyrolysis and Kuhn-Roth oxidation, proceed in high... 

Kuhn-Roth oxidation to acetic acid. From the experiment with acetate-... 

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