10.1021/ol0271988
The study presents a novel method for the reductive cleavage of triphenylmethyl (trityl) ethers using triethylsilane (Et3SiH) in the presence of a catalytic amount of triethylsilyl triflate (TESOTf) or trimethylsilyl triflate (TMSOTf). This method allows for the selective protection and subsequent cleavage of primary alcohols in the presence of acid-sensitive functional groups, which is particularly useful in carbohydrate chemistry. The reaction is mild, rapid, and highly chemoselective, with the cleavage process involving an equilibrium between trityl ether, triethylsilyl ether, and trityl cation, leading to the reduction of the trityl cation to triphenylmethane and regeneration of the silyl triflate catalyst. The study demonstrates the effectiveness of this method with a variety of 1,10-decanediol derivatives, sugar derivatives, and trehalose derivatives, showing high yields of the corresponding alcohols after mild acidic treatment. The chemicals used in the study include trityl ethers, triethylsilane, TESOTf, TMSOTf, and various protecting groups such as acetyl, pivaloyl, benzoyl, benzyl, MPM, and TBDPS, which served to protect the primary alcohols during the cleavage process.
10.1002/ejoc.201500958
The study presents a one-pot method for the formation of silyl ketene acetals and their subsequent Mukaiyama–Mannich addition to N-phenylimines, mediated by trimethylsilyl trifluoromethanesulfonate (TMSOTf) and a trialkylamine base. The process involves the conversion of thioesters into silyl ketene acetals in situ, which then react with N-phenylimines to form β-amino carbonyl compounds. The study explores the dual role of TMSOTf, acting both as a silylating agent to generate the silyl ketene acetal intermediate and as a Lewis acid to activate the imine for nucleophilic attack. A variety of chemicals were used, including thioesters, amides, esters, ketones, and N-phenylimines, serving as substrates for the reactions. The purpose of these chemicals was to demonstrate the versatility of the methodology in synthesizing complex molecules, which are structurally similar to certain cardiovascular drugs, thus highlighting the potential applications in pharmaceutical synthesis. The products were obtained as desilylated anilines without the need for a deprotection step, with yields ranging from 65 to 99%.
10.1039/b804536d
The study presents a novel and direct method for the synthesis of α-glycosyl thiols, which are compounds of significant interest in biological research and potential therapeutic applications due to their resistance to chemical and enzymatic hydrolysis. The researchers used 1,6-anhydrosugars as the starting materials and bis(trimethylsilyl)sulfide as the sulfur nucleophile, along with catalytic amounts of TMSOTf (trimethylsilyl trifluoromethanesulfonate) to facilitate the ring-opening reaction. This approach resulted in the formation of α-glycosyl thiols in high yields and with excellent stereospecificity, which is crucial for maintaining the desired anomeric configuration in the final thioglycoside products. The purpose of these chemicals was to develop a more efficient and stereoselective synthesis method for α-glycosyl thiols, which are key building blocks for constructing thioglycosides and have applications in the synthesis of various glycoconjugates.
10.1021/jo500465m
The research focuses on the development of a simple, efficient, and practical method for the synthesis of C-2 deoxy-2-iodo glycoconjugates using hypervalent iodine-mediated reactions within self-assembled structures. The purpose of this study was to explore regioselective iodination of glycals through surfactant-assembled structures, utilizing cetylammonium bromide (CTAB) and polycoordinated iodine reagents, to synthesize 2-deoxy-2-iodo acetates. The conclusions drawn from the research indicate that a fully stereoselective method for the synthesis of 2-deoxy-2-iodo glycosides has been successfully identified. The process involved the use of various chemicals, including PhI(OCOR)2, per-O-acetyl glucal, and CTAB, as well as other reagents such as Bu3SnH/AIBN for radical deiodination, and TMSOTf for intramolecular glycosidation. The study also successfully synthesized a range of 2-iodo glycosyl esters and demonstrated the potential for the synthesis of glycopolypeptides and other materials using the 2-deoxy serinyl glycosides obtained from the process.
10.1016/S0008-6215(97)00079-7
The research aimed to synthesize 4-cyanophenyl 2-azido-2-deoxy- and 3-azido-3-deoxy-1,5-dithio-β-D-xylopyranosides, which are carbohydrate derivatives with potential antithrombotic activity. The study built upon previous work by modifying the structure of beciparcil, a known antithrombotic agent, by replacing hydroxyl groups with azido groups to enhance its oral activity. Key chemicals used in the synthesis process included 3,4-di-O-benzoyl-1,5-anhydro-5-thio-D-threo-pent-1-enitol, sodium azide, ceric ammonium nitrate, trimethylsilyl triflate, and 4-cyanothiophenol, among others. The synthesized compounds were then tested for their oral antithrombotic activity in rats, with results showing that the introduction of azido groups significantly increased the activity compared to the parent compound beciparcil. However, the activity decreased upon acetylation of the amino group in the synthesized derivatives. The study concluded that compounds 3, 4, and 36 possess high oral antithrombotic activity, with the α-anomer 34 being inactive.
10.1021/ol1027267
The study focuses on the stereoelectronic effects that determine whether glycosylations proceed through oxacarbenium or α-sulfonium ion intermediates. The researchers investigated the influence of protecting groups and the constitution of the C-2 chiral auxiliary on the glycosylation pathway and the resulting anomeric outcome. They found that electron-withdrawing protecting groups, such as acetyl esters, favor the formation of α-sulfonium ions, leading to R-glycosides through an SN2-like displacement. In contrast, electron-donating protecting groups, like benzyl ethers, result in a mixture of anomers due to an equilibrium between sulfonium and oxacarbenium ions. The study also highlighted the importance of the chiral auxiliary's constitution, showing that certain substituents can enhance the stability of the sulfonium ion and promote selective glycosylation. These findings provide guidance for selecting glycosyl donors that can achieve exclusive 1,2-cis stereoselectivity in the synthesis of complex oligosaccharides.
10.3987/COM-03-S(P)20
The research aims to synthesize simplified analogs of mannopectimycins, a novel class of glycopeptide antibiotics effective against both susceptible and resistant forms of gram-positive bacteria. The study employs a combination of solid-phase and solution-phase techniques to synthesize a simplified hexapeptide. Key chemicals used include N-Fmoc-tyrosine, pentafluorophenyl trifluoroacetate, N-iodosuccinimide, trimethylsilyl triflate, HBTU, HOBt, BOP, DIPEA, and adamantanone dimethyl ketal. The synthesis process involves the assembly of a linear peptide chain on a 2-chlorotrityl chloride resin, followed by cyclization and deprotection steps. The final target compound (5) was obtained through transketalization. However, the fully synthetic analog (5) exhibited very poor antibacterial activity against a diverse panel of bacteria. The study concludes that the cyclic guanidines on the ?-hydroxyenduricidine residues play a crucial role in the antibacterial activities of mannopectimycin derivatives.
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