The structural optimization of a family of modular, enantiopure β-amino alcohol ligands with a common 2-amino-2-aryl-1,1-diphenylethanol skeleton, whose stereogenicity was introduced through the ...Jacobsen epoxidation of 1,1-diphenyl-2-arylethylenes, has led to the identification of a small set of optimal catalysts with enhanced activity and enantioselectivity in the addition of alkylzinc and arylzinc reagents to aldehydes. Criteria for the discrimination between apparently analogous, highly enantioselective ligands are proposed.
A simple and convenient methodology for the preparation of optically pure 2-amino-2-aryl-1,1-diphenylethanols is presented. Allylamine was found to produce the ring-opening of triaryloxiranes in a ...regioselective and a stereospecific fashion. Removal of the allyl protecting group provided the free 1,2-amino alcohols in enantiomerically pure form.
The lithium perchlorate-induced ring opening of (S)-triphenylethylene oxide (3) with secondary amines (piperidine (a), N-methylpiperazine (b), N-phenylpiperazine (c) and morpholine (d)) takes place ...in a stereospecific and completely regioselective manner to afford (R)-2-(dialkylamino)-1,1,2-triphenylethanols (4a − d). These amino alcohols catalytically induce the addition of diethylzinc to benzaldehyde with high enantioselectivity at 0 °C and at room temperature. Ligand 4a, which provides the highest enantioselectivity at 0 °C, has been studied in the addition of Et2Zn to a family of 20 representative aliphatic and aromatic aldehydes 5a − t. For a 17-membered set of α-substituted substrates (5a − m,q−t), including ortho-, meta-, and para-substituted benzaldehydes, the naphthaldehydes, α,β-unsaturated and aliphatic (cyclic and acyclic) aldehydes, the mean enantiomeric excess of the resulting alcohols 6a − m,q − t is 97%, whereas for three α-unsubstituted specimens (5n − p) the addition takes place with an enantioselectivity of 92−93%.
The reaction of (S)-triphenylethylene oxide (3) with diisopropoxytitanium(IV) diazide in benzene solution at 70 °C takes place readily in a completely regioselective and stereospecific manner to ...afford (S)-2-azido-1,2,2-triphenylethanol (6). Reduction of the azide by catalytic hydrogenation leads to (S)-2-amino-1,2,2-triphenylethanol (5) that, by N,N-dialkylation with 1,4-dibromobutane, 1,5-dibromopentane, 1,5-dibromo-3-oxapentane, α,α‘-dibromo-o-xylene, and methyl iodide, affords the corresponding (S)-2-dialkylamino-1,2,2-triphenylethanols (7a−e). On the other hand, the reaction of 5 with benzyl bromide or 1-iodobutane takes place as a monoalkylation, leading to the corresponding (S)-2-alkylamino-1,2,2-triphenylethanols (8f,g). The performance of amino alcohols 7a−e as ligands for the catalytic enantioselective addition of diethylzinc to benzaldehyde has been studied, with enantioselectivities of 94−97% being recorded. The best performing ligands in this family, 7a (S)-1,2,2-triphenyl-2-(1-pyrrolidinyl)-ethanol and 7c (S)-2-morpholino-1,2,2-triphenylethanol have been studied in the addition of Et2Zn to a representative family of aldehydes. With 7a, a 96.6% mean ee is recorded for a family of 16 α-substituted aldehydes and a 92.8% mean ee for a family of six α-unsubstituted aldehydes. With 7c working on the same families of aldehydes, the mean enantioselectivities are 96.8% and 91.8%, respectively.
The addition of diethylzinc to dicobalt hexacarbonyl complexes of acetylenes mediated by (R)-2-piperidino-1,1,2-triphenylethanol takes place with very high enantioselectivity (96−99% ee) to afford ...the S enantiomers of dicobalt hexacarbonyl complexes of 1-alkynyl-1-propanols. The utility of this process is exemplified by the development of a short, highly enantioselective (99% ee) synthesis of unnatural incrustoporin.
Evaluation of TLR2 and 4 in Chronic Periodontitis Ilango, Paavai; Mahalingam, Arulpari; Parthasarathy, Harinath ...
Journal of clinical and diagnostic research,
06/2016, Letnik:
10, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection due to oral bacteria. Members of Toll-Like Receptor (TLR) family ...recognize conserved microbial structures, such as bacterial lipopolysaccharides and activate signalling pathways that result in immune responses against microbial infections.
The aim of the present study was to assess the mRNA expression of Toll-Like Receptor 2 and 4 in tissues with or without chronic periodontitis.
Gingival tissue samples were collected from controls (30 subjects with healthy periodontal tissues) and experimental group (30 subjects with chronic periodontitis). Total RNA was extracted and RT-PCR was done for evaluation of TLR-2 and TLR-4. Mann Whitney U-test, Pearson Chi-square Test was used for statistics.
The results showed that there is a significant (p-value= 0.004) association between TLR-4 and the experimental group comprising of chronic periodontitis patients in comparison to the insignificant (p-value= 0.085) TLR-2 expression.
This study concludes that TLR-2 and TLR-4 expressed in the gingival tissues recognize different bacterial cell wall components thus helping us to associate its potential in diagnosing periodontal disease. Hence, in the future, these scientific findings can pave the way in using TLR as a diagnostic biomarker for periodontal disease.
Gingival diseases in childhood - a review Pari, Arul; Ilango, Paavai; Subbareddy, Venkat ...
Journal of clinical and diagnostic research,
10/2014, Letnik:
8, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Children and adolescents are subject to a wide variety of gingival infections. Epidemiological studies indicate that gingivitis of varying severity is nearly a universal finding in children and ...adolescents. The shorter life span of the primary dentition may be the reason why in general little attention is given to periodontitis in children. Since early diagnosis is important for successful treatment, it is imperative that children receive a periodontal examination as part of their routine dental visit. Furthermore destructive periodontal disease occurs in children with certain systemic diseases. Indeed the presence of severe periodontitis may be an early sign of systemic disease. A general medical evaluation to determine if systemic diseases are present should be considered in children who exhibit severe periodontitis, especially if the disease appears resistant to therapy. Though periodontal health awareness and therapy are increasing day by day in our country compared to earlier days, it is much restricted to adults rather than children. Oral cavity examination in children is much oriented in hard tissue evaluation than soft tissue health. Hence, this article enlightens about the prevalence of various soft tissue diseases and importance of long term overall oral health maintenance in childhood.
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