Synthesis of α,β-diamino acid derivatives via asymmetric Mannich reactions of glycine imino esters catalyzed by a chiral phosphoramidite·silver complex

Stereoselective Synthesis of δ- and ε-Amino Ketone Derivatives from N-tert-Butanesulfinyl Aldimines and Functionalized Organolithium Compounds

The addition of functionalized organolithium compounds derived from 5-chloro-2-methoxy-1-pentene and 6-chloro-2-methoxy-1-hexene to N-tert-butanesulfinyl aldimines imines, and a subsequent hydrolysis of the enol ether moiety, yielded different δ- and ε-amino ketone derivatives, respectively, in moderate yields and diastereoselectivities. The application of these compounds in organic synthesis was demonstrated by the preparation of 2-substituted 6-methylpiperidines in a stereoselective manner, among them natural alkaloids (+)- and (−)-isosolenopsin A.

Diastereo- and enantioselective additions of α-nitro esters to imines for anti-α,β-diamino acid synthesis with α-alkyl-substitution

The discovery that a C2-symmetric bis(AMidine) [BAM] catalyst promotes an anti-selective addition of α-substituted α-nitro esters to imines is described, providing α-substituted α,β-diamino ester products with high diastereo- and enantioselectivity. When compared to the function of a BAM catalyst reported previously, the pair offer a rare example of diastereodivergence using a bifunctional Brønsted acid-base organocatalyst.

A copper(i)-catalyzed asymmetric Mannich reaction of glycine Schiff bases with isatin-derived ketimines: enantioselective synthesis of 3-substituted 3-aminooxindoles

We have developed a copper/Ph-Phosferrox-catalyzed asymmetric Mannich reaction of Schiff bases with isatin-derived ketimines to prepare 3-substituted 3-aminooxindoles with excellent results.

Carbon Nanodots-Based Fluorescent Turn-On Sensor Array for Biothiols

Biothiols play important roles in biological processes. In this study, a novel sensor array-based method was proposed to detect and differentiate biothiols. The sensor array was constructed using three kinds of Ag⁺-sensitive carbon nanodots (CDs). The CDs were synthesized with amino acids and urea as carbon sources via a simple microwave method. Results revealed that Ag⁺ can bind with CDs and depress the fluorescence of CDs, while the subsequently joined biothiols can take Ag⁺ away from CDs and recover the fluorescence of CDs. Due to the different binding ability between Ag⁺ and various CDs, as well as Ag⁺ and various biothiols, the CD-Ag⁺ array exhibits a unique pattern of fluorescence variations when interacting with six biothiol samples (cysteamine, dithiothreitol, mercaptosuccinic acid, glutathione, mercaptoacetic acid, and mercaptoethanol). Principal component analysis (PCA) was applied to analyze the pattern and generate a clustering map for a clearer identification of these biothiols. PCA can also be employed to simplify the established three-sensor array into a two-sensor array. Both the three- and two-sensor arrays can identify these biothiols in a wide biothiol concentration range (>10 μM).

Enantioselective Silver-Catalyzed Transformations

This review collects the major progress in the field of enantioselective transformations promoted by chiral silver catalysts, covering the literature since 2008, well illustrating the power of these especially mild Lewis acid catalysts to provide novel asymmetric reactions.

First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines

The catalytic enantioselective Mannich-type reaction between glycinate Schiff base and imines has been one of the most efficient routes for accessing α,β-diamino acids. However, the glycinate Schiff bases used in the references were almost ketimines. Only several examples of aldimines were used in the presence of metal catalyst. We developed the first example of an asymmetric direct Mannich reaction using aldimines of glycinates instead of ketimines of glycinates. The reaction was well catalyzed by chiral guanidine with high yield (up to 92%) and moderate stereoselectivity (up to 65%).

Synthesis of novel polysubstituted N-benzyl-1H-pyrroles via a cascade reaction of alkynyl Fischer carbenes with α-imino glycine methyl esters

An efficient synthesis of N-benzyl-1H-pyrroles is described by a 1,4-addition/isomerization/ring closure/demetalation process of alkynyl Fischer carbene and iminoester.