74545-14-5Relevant academic research and scientific papers
Automated Quantification of Hydroxyl Reactivities: Prediction of Glycosylation Reactions
Chang, Chun-Wei,Lin, Mei-Huei,Chan, Chieh-Kai,Su, Kuan-Yu,Wu, Chia-Hui,Lo, Wei-Chih,Lam, Sarah,Cheng, Yu-Ting,Liao, Pin-Hsuan,Wong, Chi-Huey,Wang, Cheng-Chung
, p. 12413 - 12423 (2021/05/03)
The stereoselectivity and yield in glycosylation reactions are paramount but unpredictable. We have developed a database of acceptor nucleophilic constants (Aka) to quantify the nucleophilicity of hydroxyl groups in glycosylation influenced by the steric, electronic and structural effects, providing a connection between experiments and computer algorithms. The subtle reactivity differences among the hydroxyl groups on various carbohydrate molecules can be defined by Aka, which is easily accessible by a simple and convenient automation system to assure high reproducibility and accuracy. A diverse range of glycosylation donors and acceptors with well-defined reactivity and promoters were organized and processed by the designed software program “GlycoComputer” for prediction of glycosylation reactions without involving sophisticated computational processing. The importance of Aka was further verified by random forest algorithm, and the applicability was tested by the synthesis of a Lewis A skeleton to show that the stereoselectivity and yield can be accurately estimated.
Mapping mechanisms in glycosylation reactions with donor reactivity: Avoiding generation of side products
Wang, Cheng-Chung,Chang, Chun-Wei,Lin, Mei-Huei,Wu, Chia-Hui,Chiang, Tsun-Yi
, p. 15945 - 15963 (2021/01/18)
The glycosylation reaction, which is key for the studies on glycoscience, is challenging due to its complexity and intrinsic side reactions. Thioglycoside is one of the most widely used glycosyl donors in the synthesis of complex oligosaccharides. However, one of the challenges is its side reactions, which lower its yield and limits its efficiency, thereby requiring considerable effort in the optimization process. Herein, we reported a multifaceted experimental approach that reveals the behaviors of side reactions, such as the intermolecular thioaglycon transformation and N-glycosyl succinimides, via the glycosyl intermediate. Our mechanistic proposal was supported by low temperature NMR studies that can further be mapped by utilizing relative reactivity values. Accordingly, we also presented our findings to suppress the generation of side products in solving this particular problem for achieving high-yield glycosylation reactions.
Secondary amine salt catalyzed controlled activation of 2-deoxy sugar lactols towards alpha-selective dehydrative glycosylation
Ghosh, Titli,Mukherji, Ananya,Srivastava, Hemant Kumar,Kancharla, Pavan K.
, p. 2870 - 2875 (2018/05/03)
A new organocatalytic glycosylation method exploiting the lactol functionality has been disclosed. The catalytic generation of glycosyl oxacarbenium ions from lactols under forcible conditions via weakly Br?nsted-acidic, readily available secondary amine salts affects the diastereoselective glycosylation of 2-deoxypyranoses and furanoses. This operationally simple iminium catalyzed activation of 2-deoxy hemi-acetals is a potential alternative to the existing cumbersome methods that need specialized handling. The mechanisms for this unique transformation and kinetic/thermodynamic effects have been discussed based on both experimental evidence and theoretical studies.
Dehydrative glycosidations of 2-deoxysugar derivatives catalyzed by an arylboronic ester
Manhas, Sanjay,Taylor, Mark S.
, p. 42 - 49 (2018/10/26)
An N-methylpyridinium-4-boronic ester acts as a catalyst for dehydrative glycosidations of 2-deoxy sugar-derived hemiacetals. The catalytic protocol is tolerant of functionalized acceptors, including alcohols bearing isopropylidene ketal, tert-butyl carbamate or benzyl carbamate groups. The results demonstrate that organoboron-catalyzed substitution reactions of alcohols, which have previously been conducted on π-activated (benzylic, allylic or propargylic) substrates, can also be used to achieve C–O bond formation from carbohydrate-derived hemiacetals.
Facile O-glycosylation of glycals using Glu-Fe3O4-SO3H, a magnetic solid acid catalyst
Thombal, Raju S.,Jadhav, Vrushali H.
, p. 30846 - 30851 (2016/04/09)
A new glucose derived magnetic solid acid catalyst (Glu-Fe3O4-SO3H) was synthesized in a convenient and ecofriendly manner and well characterized using FTIR, PXRD, EDAX, SEM, and XPS which showed the presence of Fe3/
TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals
Hsu, Mei-Yuan,Liu, Yi-Pei,Lam, Sarah,Lin, Su-Ching,Wang, Cheng-Chung
supporting information, p. 1758 - 1764 (2016/10/05)
The thio-additions of glycals were efficiently promoted by a stoichiometric amount of trimethylsilyl bromide (TMSBr) to produce S-2-deoxyglycosides under solvent-free conditions in good to excellent yields. In addition, with triphenylphosphine oxide as an additive, the TMSBr-mediated direct glycosylations of glycals with a large range of alcohols were highly α-selective.
Organocatalytic Glycosylation by Using Electron-Deficient Pyridinium Salts
Das, Somnath,Pekel, Daniel,Neud?rfl, J?rg-M.,Berkessel, Albrecht
supporting information, p. 12479 - 12483 (2015/10/12)
A new organocatalytic glycosylation method based on electron-deficient pyridinium salts is reported. At ambient temperature and catalyst loadings as low as 1 mol %, 2-deoxyglycosides were formed from benzyl- and silyl-protected glycals and primary or secondary glycosyl acceptors, with excellent yields and anomeric selectivity. Mechanistic investigations point to alcohol-pyridinium conjugates (1,2-addition products) as key intermediates in the catalytic cycle.
The synthesis of 2-deoxy-α-d-glycosides from d-glycals catalyzed by TMSI and PPh3
Cui, Xi-Kai,Zhong, Ming,Meng, Xiang-Bao,Li, Zhong-Jun
, p. 19 - 22,4 (2020/07/30)
2-Deoxyglycosides were synthesized in high α-selectivity by the direct addition of alcohols to d-glucal and d-galactal catalyzed by TMSI and PPh3. The acid labile isopropylidene group is tolerated under this condition.
Development of an effective chiral auxiliary for hydroxyalkyl radicals
Garner, Philip,Anderson, James T.,Cox, Philip B.,Klippenstein, Stephen J.,Leslie, Ray,Scardovi, Noemi
, p. 6195 - 6209 (2007/10/03)
The development of an effective chiral auxiliary for hydroxyalkyl radicals is delineated. Both the 2-tetrahydropyranyl (THP) and tri-O-benzyl-2-deoxy-α-D-glucopyranosyl (GLU) auxiliaries resulted in diastereoselective radical additions to methyl acrylate at -78°C (ds = 6/1 and 11/1, respectively). The developing stereochemistry at the radical center was completely under auxiliary control. Correlation experiments showed that the D-GLU auxiliary led to attack on the radical Si-face. The selectivity of these radical additions dropped-off considerably when the more reactive 2-nitropropene trap was employed. Computational studies suggested that the observed facial selectivity was due primarily to entropic factors in the transition state but that a smaller temperature-dependent enthalpic contribution was also involved. It was hypothesized that incorporation of a quaternary center at C-6 (THP numbering) would restore the facial selectivity with more reactive radical traps by restricting the orientations available to the incoming alkene. In the event, the trans-6-tert-butyltetrahydropyranyl (tBu-THP) auxiliary resulted in very good diastereoselection with 2-nitropropene (ds = 35/1 at -78°C, 15/1 at 0°C, and 8/1 at RT) as did the tri-O-benzyl-6,6-dimethyl-2-α-D-deoxyglucopyranosyl (diMe-GLU) auxiliary during additions to ethyl α-trifluoroacetoxyacrylate (ds = 10/1 at 0°C). A protocol for recovery of the sugar-derived chiral auxiliaries was also established. This work sets the stage for the development of a novel approach to 1, 3, 5...(2n + 1) polyols based on iterative radical homologation as well as the application of these pyranosidic auxiliaries to other synthetically important reactions.
Tetra-n-propylammonium tetra-oxoruthenate(VII): A reagent of choice for the oxidation of diversely protected glycopyranoses and glycofuranoses to lactones
Benhaddou,Czernecki,Farid,Ville,Xie,Zegar
, p. 243 - 250 (2007/10/02)
2,3,4,6-Tetra-O-benzyl-D-glucopyranose, 2,3,5-tri-O-allyl-D-ribofuranose, 2,3,5-tri-O-allyl- and -tri-O-benzyl-D-arabinofuranose, and 2-deoxy-3,5-di- O-allyl-D-erythro-pentofuranose were oxidized to their corresponding lactones 6-10 by dimethyl sulfoxide activated by oxalyl chloride, pyridinium dichromate in the presence of molecular sieves and acetic acid, and tetra-n- propylammonium tetra-oxoruthenate(VII) using 4-methylmorpholine N-oxide as co-oxidant. With the latter reagent, analytically pure lactones were obtained in 83-98% yield. A multistep preparation of 3,4,6-tri-O-benzyl-2-deoxy-D- arabino-hexono-1,5-lactone (14) from 3,4,6-tri-O-benzyl-1,5-anhydro-2-deoxy- D-arabino-hex-1-enitol (65% overall yield) is described. 2,3,4,6-Tetra-O-benzyl-D-glucopyranose, 2,3,5-tri-O-allyl-D-ribofuranose, 2,3,5-tri-O-allyl- and -tri-O-benzyl-D-arabinofuranose, and 2-deoxy-3,5-di-O-allyl-D-erythro-pentofuranose were oxidized to their corresponding lactones 6-10 by dimethyl sulfoxide activated by oxalyl chloride, pyridinium dichromate in the presence of molecular sieves and acetic acid, and tetra-n-propylammonium tetra-oxoruthenate(VII) using 4-methylmorpholine N-oxide as co-oxidant. With the latter reagent, analytically pure lactones were obtained in 83-98% yield. A multistep preparation of 3,4,6-tri-O-benzyl-2-deoxy-D-arabino-hexono-1,5-lactone (14) from 3,4,6-tri-O-benzyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol (65% overall yield) is described.
