Recent Advances in the Synthesis of C-oligosaccharides

Abstract

This paper reviews the recent advances in the synthesis of catabolically stable sugar mimetics, Coligosaccharides. These compounds are synthetic analogs of the naturally occurring Ooligosaccharides, in which the interglycosidic oxygen has been replaced by a methylene group. This review is organized in terms of chemistry used to assemble C-oligosaccarides under the subheadings: anionic approaches, cationic methods, reductive glycosyl samarium chemistry, cyclization methodology, and free radical chemistry.

Convenient Syntheses and Transformations of 2‐C‐Malonyl Carbohydrates

“…Especially the stability of the glycosidic linkage under the oxidative and acidic conditions in the presence of MnA C H T U N G T R E N N U N G (OAc) 3 or CAN was problematic. We chose hexa-O-acetyl-d-maltal (6 j) and hexa-O-acetyl-d-lactal (6 k) as representative examples, since they are components of many naturally occurring oligosaccharides and can be easily synthesized on a large scale.…”

“…We conducted the first experiments with MnA C H T U N G T R E N N U N G (OAc) 3 to generate the malonyl radicals 5, but the acidic reaction conditions led to the partial cleavage of the glycosidic linkages.…”

“…Although many synthetic strategies for simple C-glycosides were developed over the years, [2] the preparation of Coligosaccharides is more laborious and depends on a convenient access to the corresponding C-branched monosaccharides. [3] For this purpose, carbon substituents can be easily introduced at the anomeric center, whereas C-functionalizations at other positions of the carbohydrate require many steps. Especially carboxylic acid side chains are of current interest, since they offer an elegant entry to C-oligosaccharides by ring-closing metathesis.…”

“…Therefore, we developed a simple procedure to introduce malonyl substituents at the 2-position of carbohydrates in only one step from commercially available starting materials (Scheme 1, pathway B). [7] The reaction of malonates 4 with MnA C H T U N G T R E N N U N G (OAc) 3 Abstract: 2-C-malonyl carbohydrates were synthesized in only few steps and high yields by radical additions of malonates to glycals. For the first time, the undesired formation of nitrates was completely suppressed with anhydrous cerium ammonium nitrate (CAN) as oxidizing agent.…”

Efeito da adição de precursores na produção de alcaloide anticancerígeno usando a técnica de planejamento experimental

“…[4][5][6][7] Inicialmente, este alcalóide foi extraído de sementes de plantas, 8 posteriormente, obtido a partir de culturas de células vegetais 9 e, mais recentemente, por fermentação 8,10,11 e síntese química. 12,13 Entretanto, esta última técnica, embora seja a de maior expansão, tem apresentado problemas referentes a seu elevado custo e baixo rendimento na produção, com grande número de operações e etapas de síntese, unido à formação de misturas racêmicas que dificultam a purificação e recuperação do produto final. 14 De fato, embora existam algumas propostas para a síntese química assimétrica deste alcalóide, são requeridas ainda múltiplas etapas de reação, prevalecendo os altos custos do processo.…”