Decarboxylation product

The decarboxylated products are obtained directly, however, if condensation of tryptamine with the a-oxo acid is carried out in aqueous solution at elevated temperature. This direct synthesis of a l-substituted-l,2,3,4-tetrahydro-j8-carboline has been carried out with... 

Fischer indolization of 9-arylhydrazono-6,7,8,9-tetrahydro-4//-pyrido-[l,2-u]pyrimidin-4-ones 289 by heating in 85% phosphoric acid, or in PPA yielded 7,12-dihydropyrimido[l, 2 l,2]pyrido[3,4-Z)]indol-4(6//)-ones 290 (96JHC799, 99MI12, 00MI22). From the 3-ester and 3-carboxylic acid derivatives 289 (R = COOEt, COOH) and decarboxylated products 290 (R = H) were obtained. 

The decarboxylated product 4 can also be prepared in one step, in 36% yield, starting from the a-hydrazone of the free benzoylglyoxylic acid 1 (R1 = C02H, R2 = Ph) by heating to 120-130 C.18... 

In Oxalobacter formigenes, oxalate and its decarboxylation product formate form a one-to-one antiport system, which involves the consumption of an internal proton during decarboxylation, and serves as a proton pump to generate ATP by decarboxylative phosphorylation (Anantharam et al. 1989). 

The oxidation of wood charcoal by means of sulfuric acid leads to mellitic acid and its decarboxylation products 6 nitric add may also be employed.7 Pyromellitic acid has also been obtained by the electrolytic oxidation of graphite in an alkaline medium.8... 

The substitution, with cyclic amines, of a 4-fluoro atom in 50 (R= Et, R1 = F) was unsuccessful at 80-120 °C, probably because of the presence of an acidic CH2 group at position 3 <1995T11125>. 3-Decarboxylated products 50 (R = Et) were prepared from 49 (R = Et) under different reaction conditions (Equation 7) < 1995T11125>. Direct conversion of 49 (R= Et R1 = Et, allyl) to acid 50 (R = H, R1 = F) was achieved in a boiling mixture of AcOH-conc. HC1 <1995T11125>. 

Treatment of 3-(2-pyrrolidino)pyridine with 2 molar equiv of diethyl acetylenedicarboxylate under microwave conditions gives the tetrahydropyrrolonaphthyridine 283 and (presumably) diethyl maleate or fumarate. Under conventional heating conditions, decarboxylated products are also observed (Scheme 71) <2005TL3953>. 

The irreproducibility (98,100) of the Pesci decarboxylations [Eqs. (84) and (86)] (97,99) has further implications since the decarboxylation products were claimed to undergo novel nucleophilic displacements of mercury (96,97,99). Some reported nucleophilic demercurations of an authentic mercurial (96) could not be repeated (98). A Pesci type hemidecarboxylation of 5-norbornene-2,3-dicarboxylic acid has been reported by Takahashi (101), but this has also been found to be irreproduci-ble (101a). 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

Since tryptophan (and its decarboxylation product, tryptamine) serve as precursors in many synthetic and biosynthetic routes to /J-carbolincs, it is not surprising that C-1 of the /J-carbolinc ring is the most common site of substitution (as it is the only ring atom of the /J-carbolinc ring system not derived from tryptophan). Indeed, this is the only site of substitution for many /J-carboline natural products. Two examples of naturally occurring /J-carbolines substituted only at C-1 which possess antitumor activity are manzamine A and manzamine C (Fig. 2). Owing to its greater simplicity and nearly equal antitumor activity, most initial synthetic efforts were directed toward manzamine C [11,12]. 

Abbott et al. [163] described a pyrolysis unit for the determination of Picloram and other herbicides in soil. The determination is effected by electron capture-gas chromatography following thermal decarboxylation of the herbicide. Hall et al. [164] reported further on this method. The decarboxylation products are analysed on a column (5mm i.d.) the first 15cm of which is packed with Vycor chips (2-4mm), the next 1.05m with 3% of SE-30 on Chromosorb W (60-80 mesh) and then 0.6m with 10% of DC-200 on Gas Chrom Q (60-80 mesh). The pyrolysis tube, which is packed with Vycor chips, is maintained at 385°C. The column is operated at 165°C with nitrogen as carrier gas (110ml min-1). The method when applied to ethyl ether extracts of soil gives recoveries of 90 5%. Dennis et al. [165] have reported on the accumulation and persistence of Picloram in bottom deposits. 

Labeling experiments with l-deoxy-l-(dibenzylamino)-D-[l- C]-aruI>-mo-2-hexulosuronic acid [l- C] 112 indicated that the C label corresponded to the 5-methyl group of 111 (see Ref. 234). This is also consistent with a l-deoxy-2,3-dicarbonyl intermediate (115), and indicates that 111 is a decarboxylation product (see Scheme 22). The precise step entailing decarboxylation has not yet been determined. The carboxyl group could be carried through to ring closure (furanone formation). Such a step would provide a 2-carboxylate which is a /3-keto acid subject to ready decarboxylation. The labeling information and the initial steps of the mechanism in Scheme 22 are also consistent with the formation of 111 from D-[l- C]ribose and a secondary amine. ... 

This observation led to the suggestion that the reacting nucleophile is a tautomer of the anion that is initially formed rather than its decarboxylation product ... 

Most people have heard of antihistamines, even if they have little concept of the nature of histamine. Histamine is the decarboxylation product from histidine, and is formed from the amino acid by the action of the enzyme histidine decarboxylase. The mechanism of this pyridoxal phosphate-dependent reaction will be studied in more detail later (see Section 15.7). 

Dopamine is the decarboxylation product of DOPA, dihydroxyphenylalanine, and is formed in a reaction catalysed by DOPA decarboxylase. This enzyme is sometimes referred to as aromatic amino acid decarboxylase, since it is relatively non-specific in its action and can catalyse decarboxylation of other aromatic amino acids, e.g. tryptophan and histidine. DOPA is itself derived by aromatic hydroxylation of tyrosine, using tetrahydrobiopterin (a pteridine derivative see Section 11.9.2) as cofactor. 

The N(4) atom of the side-chain piperazino group of 187 (R = Et, R = piperazino) was acylated with di-/cr/-butyl oxalate. 3-Decarboxylated products (187) were prepared from 186 under different reaction conditions in 44-81% yield (see Scheme 4) [95T11125]. The ester group of 187(R = Et) was hydrolyzed in boiling acetic acid in the presence of concentrated hydrochloric acid to give 3-carboxylic acids (187, R = H). 

The advantage of these reaction conditions became more obvious with the enyne 11, in which the reacting olefin is attached to an electron-withdrawing substituent. As mentioned earher, the decarboxylation product 21 of the initially formed keto ester 21 was the major product, due to the prolonged reaction time (Eq. 3). Gratifyingly, when the reaction was carried out under a reduced pressure of CO, the reaction time was significantly reduced to facilitate the isolation of the keto ester 21 as the major product (Eq. 9). 

Traces of the decarboxylation product were obtained (70JHC247). The rearrangement proceeded efficiently in sulfuric acid. 

Problem 16.18 (a) Suggest a mechanism for a ready decarboxylation of malonic acid, HOOCCH,COOH, that proceeds through an activated, intramolecular H-bonded, intermediate complex, (b) Give the decarboxylation products of (i) oxalic acid. HOOC—COOH, and (ii) pyruvic acid, CHjCOCOOH. 

The first porphyrin intermediate of the biosynthetic pathway is uroporphyrinogen, which is stepwise decarboxylated by uroporphyrinogen decarboxylase to heptacarboxy-, hexacarboxy-, pentacarboxy-, and coproporphyrinogen. This latter compound proceeds, as indicated in Fig. 7.3.1, to protoporphyrinogen and protoporphyrin. The oxidized uroporphyrin and its decarboxylation products up to coproporphyrin are assayed in urine. Coproporphyrin and the further downstream intermediaries can be recovered from feces as described below. 

Porphyrins in plasma are mainly used to distinguish between PCT and pseudoporphyria in patients with chronic hemodialysis. CEP patients also show characteristic elevations with dominance of I-isomers, especially of uroporphyrin and its decarboxylation products, in both plasma and erythrocytes. Plasma porphyrins may be used for follow-up of the patients. 

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