Desymmetrization of Cyclic Sulfonimidamides by Asymmetric Allylation.

Herein we report the first transition metal-catalyzed approach to the enantioenriched synthesis of cyclic sulfonimidamides relying on commercially available palladium catalysts and ligands. High-throughput experimentation (HTE) was employed to identify the optimal catalyst system and solvent. The method is applied to a variety of saturated and unsaturated rings and exhibits the highest selectivity for 2-substituted allyl electrophiles. The products are further elaborated to complex, tricyclic scaffolds. DFT experiments presented herein highlight the key ligand substrate interactions leading to the high levels of enantioselectivity.

Diastereoselective Addition of Prochiral Nucleophilic Alkenes to α-Chiral N-Sulfonyl Imines.

The Lewis-acid-promoted addition of prochiral E- and Z-allyl nucleophiles to chiral α-alkoxy N-tosyl imines is described. Alkene geometry is selectively transferred to the newly formed carbon-carbon bond, resulting in stereochemical control of C1, C2, and C3 of the resulting 2-alkoxy-3-N-tosyl-4-alkyl-5-hexene products. A computational analysis to elucidate the high selectivity is also presented. This methodology was employed in the synthesis of two naturally occurring isomers of clausenamide.

1,3-Asymmetric Induction in Diastereoselective Allylations of Chiral N-Tosyl Imines.

Lewis acid mediated allylations of ß-alkoxy N-tosyl imines using allyltrimethylsilane lead to 3-alkoxy homoallylic N-tosyl amines with anti-selectivity. Two methods of Cu(OTf)2-mediated allylations are reported herein, demonstrating that diastereoselectivity can be achieved through 1,3 acyclic stereocontrol of ß-chiral aldimines. Observed selectivity trends and computational evidence suggest selectivity arises through the formation of a six-membered ring chelate. The product ratios of these allylations are dependent on conformational preferences of the chelate and steric effects in the transition-state structures.

Evaluation of Platelet Rich Fibrin Obtained Using Different Centrifugation Parameters as a Tool for Regenerative Medicine.

BACKGROUND: Platelet-rich fibrin (PRF) is a biomaterial widely used in the field of regenerative medicine. The purpose of this work was to analyze the structure and biomolecular characteristics of PRF through nine centrifugation parameters (CP) for its preparation, using a pool of blood samples of five volunteers. METHODS: The PRF obtained was analyzed by morphological and histological characteristics, as well as electronic and atomic force microscopy and growth factors determinations. RESULTS: A longer time of centrifugation showed taller clots and denser mesh fibrin in comparison with a short time (p < 0.05). The protocols with higher speed of centrifugation showed higher levels of PDGF-BB and VEGF. Higher levels of TGFß1 were found in protocols with a shorter centrifuge time. The mean platelet count (916.05 ± 23.73 cells x 103 cells x cm3) and its roughness (Ra) (616.5 ± 45.2 nm) did not show significant differences between different CP (p > 0.05). A significant correlation between fibrin density and levels of PDGF (r = 0.57) and VEGF (r = 0.52) was found. Additionally, the size of the clot had a significant correlation (r = -0.47) with TGFß1 levels. CONCLUSIONS: Different centrifugation parameters to obtain PRF have been reported. These results indicate that changes in the conditions to obtain PRF have a significant impact on their fibrin structure, cellular distribution, and biomolecular content, which can be decisive for its choice in the different clinical applications to be used. It is necessary to use a standardized centrifuge and protocol to guarantee high-quality PRF and clinical outcomes with less variability.

Root Coverage with Platelet-Rich Fibrin in Miller's Class I, III, and IV Gingival Retractions.

Coronally advanced flap (CAF) with connective tissue graft (CTG) is considered as the most predictable method to treat Miller's Class I and II gingival recessions (GR). However, due to the patient's postsurgical discomfort, the difficulty of finding a donor with an adequate tissue thickness, the high costs of acellular dermal substitute among others, the platelet concentrates have been found to scaffold alternative to replace CTG as a part of the CAF treatment for GR. Nevertheless, according to the recent literature, the evidence of success in Class III and IV has been limited for CAF and platelet-rich fibrin (PRF). The purpose of this report is to present a case of multiple Miller's Class III and IV GR treated with CAF and PRF where the potential of PRF to increase gingival thickness and clinical attachment level, and improve soft-tissue healing and clinical appearance was corroborated.

Palladium-Catalyzed Direct C(sp2)-H ortho-Arylation of Anilides Using 2-Aminophenylpyrazole as the Directing Group.

Palladium-catalyzed ortho-arylation of anilides was achieved using 2-aminophenyl-1H-pyrazole (2-APP) as a new directing group. Using Pd(OAc)2 as the catalyst and AgO as the promoter, mono- and diarylation of anilides were realized in up to 89% isolated yield. Further manipulation of the arylation product may be accomplished by a 2-step sequence involving an acidic hydrolysis of the methylated amide. More interestingly, in the presence of K2CO3, tandem C-C/C-N cyclization products were obtained for a couple of substrates.

2-Aminophenyl-1H-pyrazole as a Removable Directing Group for Copper-Mediated C-H Amidation and Sulfonamidation.

2-Aminophenyl-1H-pyrazole was discovered as a removable bidentate directing group for copper-mediated aerobic oxidative C(sp(2)-H) bond amidation and sulfonamidation. When Cu(OAc)2 was employed as the copper source and 1,1,3,3-tetramethylguanidine as an organic base, the reaction, optimally carried out overnight in DMSO at 80 °C in open air, produced a variety of amides and sulfonamides in moderate to excellent yields. This directing group has proven to be particularly efficient in C-H sulfonamidation.

First Insights into the Genome of the Amino Acid-Metabolizing Bacterium Clostridium litorale DSM 5388.

Clostridium litorale is a Gram-positive, rod-shaped, and spore-forming bacterium, which is able to use amino acids such as glycine, sarcosine, proline, and betaine as single carbon and energy sources via Stickland reactions. The genome consists of a circular chromosome (3.41 Mb) and a circular plasmid (27 kb).