The Methylpyrroles. Synthesis and Characterization

Hinman, R. L.; Theodoropulos, S.

doi:10.1021/jo01046a030

Cited by 90 publications

(23 citation statements)

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“…A novel pyrroleninone cross-link from bovine dentin This behavior is consistent with that published for pyrroles (Chiang and Whipple, 1963;Hinman and Theodoropulos, 1963;Bullock, 1958;Cookson, 1953). The instability of IV may be explained by reactions of the substituents of the pyrrole ring: Scissions in the alkyl chain attached to the nitrogen of the ionized pyrrole ring have been reported previously (Duffield et al, 1965).…”

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confidence: 88%

Reactions of the organic matrix in dentin caries

Kleter¹

2003

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A tooth consists of pulp tissues encased in hard, mineralized tissues. Dentin-forming cells (odontoblasts) are found at the border of the pulp. Odontoblasts have extensions running centripetally through narrow channels (tubules) in predentin and dentin, a bone-like tissue. Predentin is deposited by odontoblasts and consists of organic matrix. Mineralization takes place some time after the predentin deposition, thus at some distance from the odontoblast. Mineralization of the organic matrix is induced by enzymes and proteins secreted by the odontoblast extensions into the predentin at the level of the mineralization front. The tubules end in the outer part of dentin (mantle dentin), the composition of which deviates from bulk dentin. Dentin consists of mineral (70 wt%), water (10 wt%) and organic matrix (20 wt%). At the tooth's crown, dentin is lined with enamel, a mineralized tissue with far less of an organic matrix than dentin. Normally only a part of the crown is exposed to the oral cavity. Root dentin is lined with cementum, a thin layer of partially mineralized tissue containing organic material. The cementum near the root apex is of a cellular nature, but becomes increasingly acellular towards the crown. The tooth is set in the alveolar ridge of the jaw, and is encircled by the periodontal ligament, which helps absorb the mechanical forces exerted on the tooth. Above the alveolar bone, the tooth is covered by soft, gingival tissue.Dentin organic matrix. The organic matrix of dentin consists of collagen for 90 wt%. Non-collagenous compounds comprise proteoglycans, highlyphosphorylated proteins, osteonectin, osteocalcin, dentin sialoprotein, and lipids (Boskey, 1989; Butler et al., 1992; Goldberg and Septier, 1985; Linde, 1989). Several non-collagenous compounds play a role in dentin formation and mineralization.Collagen is the most prevalent protein in the human body. Nineteen types of collagen have been described. The common feature is the triple helix: three polypeptide chains (α) coiled around each other. It is essential that glycine occupies each third position in the α chains. High contents of hydroxyproline stabilize the structure. Type I collagen prevails in dentin. Its molecules have 300-nm-long rod shapes, containing triple helices (1011 residues per α chain) flanked by short non-helical ends (6-25 residues per α chain). Fibrils are evenly-spaced, linearly-aligned, cylindrical groupings of molecules. The fibrils show alternating bands in electron microscopy due to the overlapping of negatively charged 7 molecule segments stained by heavy metal ions, yielding a specific "banding pattern". Parallel fibrils are gathered into fibres (Van der Rest and Bruckner, 1993).Type V collagen has been found in dentin (Lukinmaa and Waltimo, 1992) and is involved in fibril formation. Some peculiarities have been noted for dentinal type I collagen. For example, a high content of α 1 chains in rat dentin indicates the presence of molecules composed of three α 1 chains apart from the usual (α 1 ) 2 α 2 composition...

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confidence: 88%

Reactions of the organic matrix in dentin caries

Kleter¹

2003

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“…The addition of one equivalent of hexamethylphosphoric triamide improved the ratio of the desired 2-(4) over the undesired 5-isomer (5) to 60:40 at -26°C. For comparison, the Vilsmeier-Haack formylation of 3-methylpyrrole gave a 4 : 1 ratio of 2-and 5-substitution (8,9). The combination of the steric and electronic effects of the acetic ester group results in the less favorable ratio, as in the cyanation of the 3-acetic ester (1).…”

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confidence: 99%

Pyrrole chemistry. XXVII. 2,3,4-Trisubstituted pyrroles and a second synthesis of porphobilinogen from pyrrole

Faber¹,

Anderson²,

Loader³

et al. 1984

Can. J. Chem.

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Changes in some of the key intermediates and procedures used in our earlier total synthesis of porphobilinogen from pyrrole that improve the yield to 11% are reported. Ethyl pyrrole-3-acetate was formylated by the Vilsmeier-Haack method and then iodinated. The desired 2,3,4-substituted pyrrole isomer was isolated in moderate yield and, after conversion of iodide to acrylate and aldehyde to aldoxime, reduction and work-up afforded porphobilinogen lactam ethyl ester. Hydrolysis of the latter gave porphobilinogen in ten steps from pyrrole.KURT FABER, HUGH J. ANDERSON, CHARLES E. LOADER et ANNETTE S. DALEY. Can. J. Chem. 62, 1046(1984.Grlce a des changements dans quelques intermtdiaires cles et dans quelques-unes des proctdures utilisees dans notre synthkse totale anterieure du porphobilinogkne 2 partir du pyrrole, il est possible d'amdiorer le rendement a I 1%. On a formylC le pyrroleacttate-3 d'Cthyle par la mtthode de Vilsmeier-Haack et on I'a alors iodt. L'isomkre dtsire du pyrrole substituC en 2,3,4 est isolt avec un rendement modtre; aprks conversion de I'iodure en acrylate, et de I'aldthyde en aldoxime, une reduction et une extraction permettent d'isoler I'ester Cthylique de la lactame du porphobilinogkne. L'hydrolyse de ce dernier conduit au porphobilinogine en dix ttapes 2 partir du pyrrole.[Traduit par le journal]We have recently reported a total synthesis of porphobilinogen (I), the precursor of naturally occurring porphyrins and corrins, in nine steps from pyrrole with an overall yield of about 6% (1). In that synthesis, reduction of the cyanide group led to the partial reduction of the pyrrole ring and was a major factor in reducing the yield. Attempts to develop a better procedure for this reduction, using as a model the readily available 4-carbethoxyvinylpyrrole-2-carbonitrile (see the experimental section), failed. The model appeared more susceptible to ring reduction than the porphobilinogen precursor itself under most conditions. A variation on the earlier synthesis provides both a marked increase in the overall yield of porphobilinogen and also further demonstrates the versatility ofthis approach to the synthesis of 2,3,4-trisubstituted pyrroles, a type sometimes used as porphyrin building blocks (2). The steps by which a labelled carbon or nitrogen atom could be introduced into the eventual -aminomethyl side chain are also simplified.A general outline of this approach is given in Scheme 1, and follows the philosophy outlined in the earlier paper (1). The aldoxime rather than the cyanide group was used as a precursor to the aminomethyl side chain and the lactam ethyl ester of porphobilinogen (2) was the desired final intermediate.:This synthetic approach began, as did the earlier one, with the preparation of ethyl pyrrole-3-acetate (3) in three steps from pyrrole (1). Attempts to improve this synthesis by using the Wilgerodt-Kindler rearrangement of the readily available (3, 4) 3-acetyl-1-phenylsulfonylpyrrole failed. Although the rearrangement was successful, the yield of the corresponding morpho...

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“…Hinman and Theodoropulos found that 2-and 3-methylpyrroles could be resolved on Perkin-Elmer type O column at 70°C in 12 and 13 min, respectively. 168 Griffin and Obrycki also reported on the separation of 2-and 3-methylpyrroles, pyrrole, and two unidentified methylated pyrroles on a 30% Carbowax 20M on Chromosorb P (60-80 mesh) column programmed from 50 to 150°C. 169 130-190°C.…”

Section: Pyrroles and Indolesmentioning

confidence: 99%