Proline pyrrole-2-carboxylic acid

Prolines.1 The complex 2 undergoes base-catalyzed (CH,ONa) Michael addition to a,p-enals and -enones. Reaction of 2 with acrolein furnishes a dihydro-pyrrole-2-carboxylic acid which is reduced to (S)-proline. 

In the light of these studies, it has been proposed that both proline and ornithine can be converted to pyrrole-2-carboxylic acid prior to halogenation subequently amide formation by reaction with 3-amino-l-(2-aminoimidazolyl)-prop-l-ene, derived from histidine, generates oroidin, followed by cyclization to stevensine (Scheme 10.3). 

Pinho e Melo and co-workers heated a diastereomeric mixture of (2R,4R)- and (25,4/ )-2-phenylthiazolidine-2-carboxylic acids 114 with acetic anhydride in the presence of DMAD to afford pyrrolothiazole 115 in good yield and 99% ee (Fig. 4.40). Robba and co-workers synthesized the 2-azapyrrolo[l,2-a]indole ring system via a munchnone cycloaddition strategy. Trapping the munchnone derived from proline derivative 116 gave pyrrole 117 in 75% yield (Fig. 4.41). Further elaboration yielded the desired 118 and subsequent target compounds. 

Due to poor reactivity, aryl amines normally require higher reaction temperatures than aliphatic amines to ensure good conversion. In early studies, phenathroline and its Cu(I)-complex were used in the arylation of aryl amine [10, 11], but they were only applicable to the synthesis of triarylamine from secondary aryl amines. L-Proline (LI) promoted Cul-catalyzed arylation of primary aryl amines took place at 90°C (Table 9.1, entry 1) [3]. However, only electron-rich anilines gave complete conversion, while electron-deficient anilines provided low yields. Fu found that this drawback could be overcome by heating at 110°C and using pipecolinic acid (L5) as a ligand (entry 2) [12]. Similar studies were reported by Liu and coworkers in which DMEDA (Lll) was found to be a better ligand (entry 3) [13], Recently, Buchwald reported that pyrrole-2-carboxylic acid (L6) [14] is an efficient promoter for the synthesis of diarylamines (entry 4) (Table 9.3). 

H-Pyrrole-2,5-dione, 1,T-(phenylene) bis-. See m-Phenylenedimaleimide IH-Pyrrole, 1-(2-furanylmethyl)- Pyrrole, 1-furfuryl-. See 1-Furfuryl-1H-pyrrole 2-Pyrrolidine carboxylic acid Pyrrolidine-2-carboxylic acid. SeeL-Proline 2,5-Pyrrolidinedione. See Succinimide... 

Liu and coworkers have recently published the synthesis of (3) and (4), as well as several other fluorinated pyrrole analogues (not shown), by aminofluorination of allenes the synthetic approach is shown in Scheme 3 [15], This strategy takes advantage of a selective, silver-catalyzed intramolecular fluorination reaction, but the approach works best with substrates that possess electron-withdrawing R -groups on the 3-position. Because of this limitation, the yield of (3) is significantly higher than (4), 80 % versus 28 %, respectively. 4-Fluoro-pyrrole-2-carboxylic acid (5a, Fig. 2), synthesized from a fluorinated proline, was explored as a potential intermediate on the route to (3), but only extensive decomposition products were observed when (5a) was subject to flash pyrolysis [16]. 

Table II summarizes those amino acids that contain more than an un-reactive aliphatic chain, namely a reactive site which may be a functional group in the traditional sense such as sulfhydryl, thiomethyl, hydroxyl, carboxyl, carbamide, amino, or guanido, or may be an activated aromatic ring or heterocycle such as the phenolic part of tyrosine, the pyrrole unit in troptophan, and the imidazole part in histidine. Phenylalanine would only be considered in this connection as the reactive di- or tetrahydro derivative ring. iV-Peptides derived from proline and hydroxyproline are in a separate class because they are tertiary amides carrying no proton at the nitrogen atom. It may be possible to utilize this special feature for a preferential cleavage under proper conditions.

CAS 28874-51-3 (L) 54571-67-4 (DL) EINECS/ELINCS 249-277-1 (L) 259-234-9 (DL) Synonyms 5-Oxo-DL-proline, sodium salt 5-Oxo-L-proline, sodium salt PCA-Na PCA Soda Sodium 5-oxo-L-prolinate Sodium pyroglutamate Sodium DL-2-pyrrolidone-5-carboxylate Sodium L-2-pyrrol idone-5-carboxyl ate Definition Sodium salt of pyroglutamic acid... 

Effective pathway towards 3-fluoropyrrole 37 was elaborated on the base of easily available methyl tranv-4-hydroxy-L-prolinate 32. After Boc-protection of this compound followed by oxidation with PDC, ketone obtained 34, was converted into difluoride 35 by the reaction with DAST. N-Boc deprotection of 35 with trifluoroacetic acid afforded, after basic treatment, free base 36 which was aromatized by activated manganese dioxide into methyl 4-fluoro-lH-pyrrole-2-carboxylate 37 [15, 19],... 

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