Pyrrole-3-carboxylate

Other Methods. Newer methods for forming pyrrole and related heterocyctic rings iaclude the formatioa of substituted pyrrole 2-carboxylate esters by coadeasatioa of P-dicarboayl compouads with glyciaate esters (25). 

The main feature of the reactivity of pyrrole-2-carboxylic acids is the ease with which the carboxyl group is removed. Thermal decarboxylation is a preparatively useful reaction. 

The base-promoted ring contraction of 3-bromo-2-pyrones to 2-furoic acids cf. Scheme llOd) is a well exemplified reaction 01CB1992,69JCS(C)1950,73JCS(P1)1130> which has also been applied to the obtention of benzofuran-2-carboxylic acids frorn 3-bromocoumarins 08CB830,70KGS(S2)166), Similar base treatment of 3-amino-2-pyrones provides pyrrole-2-carboxylic acids (Scheme IlOe) 75JHC129). 

H-Pyrrole-2-carboxylic acid, methyl ester H NMR, 4, 166 (75UP30400)... 

H-Pyrrole-2-carboxylic acid, 4-ethyl-3-methyl-5-thienoyl-, ethyl ester X-ray, 4, 160 (78AX(B)2929> lH-Pyrrole-2-carboxylic acid, 5-methyl-, ester X-ray, 4, 160 (76T2057)... 

Pyrrole-2-carboxamide, N,N-dimethyl-conformation, 4, 194 Pyrrole-3-carboxamide, N,N-dimethyl-conformation, 4, 194 Pyrrolecarboxamides synthesis, 4, 242 Pyrrole-2-carboxamides synthesis, 4, 148, 360 Pyrrolecarboxylhydrazides Curtius degradation, 4, 362 Pyrrole-2-carboxylic acid, l-benzyl-3-hydroxy-ethyl ester... 

Pyrrole-2-carboxylic acid, 4,5-dimethyl-ethyl ester formylation, 4, 217 Pyrrole-2-carboxylic acid, 3-hydroxy-... 

Michael addition reactions, 4, 302 reactions with ally halides, 4, 301 Pyrrole-2-carboxylic acid, 1-methyl-conformation, 4, 194 esters... 

Thieno[3,2-6]pyrrole-2-carboxylic acid, 5-aryI-synthesis, 4, 819... 

FIGURE 16.7 The proline racemase reaction. Pyrrole-2-carboxylate and A-l-pyrroline-2-carboxylate mimic the planar transition state of the reaction. 

Benzyl isocyanoacetate is a nsefnl reagent for the preparadon of benzyl 5-nnsnbsdnited pyrrole-2-carboxylates, which are widely used In the synthesis of porphyrins." Ono and coworkers have prepared pyrroles snbsdnited with various snbsdnients at the fi-posidons."" Because the reqidsite fi-nitro acetates for nitroalkenesi are readily available by the Henry... 

The synthesis is straightforward because for the preparation of the tetrapyrranc a bipyrrole can also be used as a central unit to which a benzyl 5-(acetoxymethyl)pyrrole-2-carboxylate can be attached as the terminal pyrrole rings. Debenzylation by catalytic hydrogenation then gives the desired tetrapyrrane building block 68. 

S-[l[/ (R )],2a,3a(i,6ap]]-l-[2-[[l-(ethoxycarbonyl)-3-phenylpropyl]amino]-l-oxopropyl]octahydrocyclopenta[6]pyrrole-2-carboxylic acid... 

The related planar pyrrole analog 118 has also been prepared (2) from either ethyl or benzyl pyrrole-2-carboxylate 116. Direct alkylation with diethyl phosphonomethyl triflate (70) and base produced the N-phosphonomethylpyrrole 2-carboxylate 117, which was deprotected with trimethylsilyl bromide and saponified to the corresponding phosphonic acid 118. 

Non-oxidafive novel aromatic acid decarboxylases, pyrrole-2-carboxylate decarboxylase and indole-3-carboxylate decarboxylase, were found in Bacillus... 

Pyrrole-2-carboxylate decarboxylase attains equilibrium in the course of either decarboxylation or carboxylation (Fig. 8). The decarboxylation of 100 mM pyrrole-2-carboxylate was in equilibrium after Ih, resulting in an equilibrium constant of 0.3 M." Due to this balanced equilibrium, the enzyme also catalyzed the reverse carboxylation of pyrrole after the addition of HCO3, leading to a similar equilibrium constant of 0.4 M and a shift of the [pyrrole]/[pyrrole-2-carboxylate] ratio toward the acid. 

Figure 8 Decarboxylation of pyrrole-2-carboxylate (a) and carboxylation of pyrrole (b) by pyrrole-2-carboxylate decarboxylase.

Pyrrole-2-carboxylate is employed in the synthesis of various pharmaceuticals" and a potential herbicide. A number of organic syntheses have been described " However, they require multiple steps and result in low yields. Furthermore, the chemical carbonation of pyrrole with K2CO3 depends on high pressure and temperature. The one-step enzymatic conversion has advantages with regard to regiospecificity, yield, and mild reaction conditions. 

The carboxylafion of indole into indole-3-carboxylate was observed by the purified indole-3-carboxylate decarboxylase as well as by the whole cells. For the carboxylafion reaction, temperatures over 30°C were not appropriate. The activities at 10, 20, and 30°C were about the same. The activity was maximal at pH 8.0 (Tris-HCl buffer, 100 mM). As shown in Fig. 10, the resting cells of A. nicotianae F11612 also catalyzed the carboxylafion of indole efficiently in the reaction mixture containing 20 mM indole, 3M KHCO3, 100mM potassium phosphate buffer (pH 6.0) in a tightly closed reaction vessel. By 6h, 6.81 mM indole-3-carboxylic acid accumulated in the reaction mixture with a molar conversion yield of 34%. Compared to the carhoxylation of pyrrole by pyrrole-2-carboxylate decarboxylase, the lower value compared might derive from the lower solubility of indole in the reaction mixture. 

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