Regioselective chemoenzymatic syntheses of ferulate conjugates as chromogenic substrates for feruloyl esterases

• Olga Gherbovet,
• Fernando Ferreira,
• Apolline Clément,
• Mélanie Ragon,
• Julien Durand,
• Sophie Bozonnet,
• Michael J. O'Donohue and
• Régis Fauré

Beilstein J. Org. Chem. 2021, 17, 325–333, doi:10.3762/bjoc.17.30

• chromogenic 5-O-feruloylated α-ʟ-arabinofuranosides 1a and 1b is usually achieved using a multistep pathway that involves trapping the furanose conformation, anomeric activation, glycosidation, regioselective deprotection of the primary hydroxy group, feruloylation, and final deprotection to yield the target

Carbonylonium ions: the onium ions of the carbonyl group

• Daniel Blanco-Ania and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2018, 14, 2568–2571, doi:10.3762/bjoc.14.233

• glycosidation reactions take place [6]. “Oxacarbenium ions” [7][8][9][10][11], “oxocarbenium ions” [12][13][14][15][16], “oxycarbenium ions” [17][18][19][20][21], and “carboxonium ions” [22][23] are the most extended terms among the different names found in the literature for these intermediates in this and

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• synthesis of various jadomycins [54]. Whereas the Mitsunobu glycosidation of 68 with the phenolic aglycon 70 yields the pure 1,2-trans-glycoside 71, the 2-deoxy sugar 69 yields the glycoside 72 as a 6:1 α,β-anomeric mixture (Scheme 11). In contrast to this, the jadomycin B carbasugar analogue 75 was formed

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• ester glycosides were considered to have self-assembled structures suitable for intramolecular glycosylation. As depicted in Figure 9, treatment of 184 with TMSOTf first cleaved the silyl ether to form 185, which was correctly positioned to undergo intramolecular glycosidation. As a result, the Lewis

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• latter reaction rapidly decomposed during work-up in solution. Regioselective and stereoselective glycosidation of adenine, N6-benzoyladenine, N4-benzoylcytosine, thymine and uracil to the corresponding β-N9-purine or β-N1-pyrimidine ribosides was achieved on gram scales under Vorbrüggen-type conditions

• conditions. The capacity for stereoselective glycosidation, rapid phosphate coupling in the presence of water and also formation of specific base-pairing interactions have all been demonstrated in a ball mill and may facilitate understanding of the early appearance of life in the Hadean/Archean Eon

• in a MBM. Thiolate displacement reactions of nucleoside derivatives in a MBM. Selenocyanate displacement reactions of nucleoside derivatives in a MBM. Nucleobase glycosidation reactions and subsequent deacetylation performed in a MBM. Regioselective phosphorylation of nicotinamide riboside in a MBM

AuBr₃-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

• Jayashree Rajput,
• Srinivas Hotha and
• Madhuri Vangala

Beilstein J. Org. Chem. 2018, 14, 682–687, doi:10.3762/bjoc.14.56

• coordination of AuBr3 with the amide. Having successfully accomplished the gold(III)-catalyzed azido glycosidation of per-O-acetates, we next turned our attention to per-O-benzoylated sugars. Gratifyingly, using 12 mol % AuBr3, the easily accessible per-O-benzoylated mannopyranose and glucopyranose (Table 2

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone

• Kai Zhang,
• Shenglan Liu,
• Anjun Liu,
• Hongxin Chai,
• Jiarong Li and
• Lamusi A

Beilstein J. Org. Chem. 2017, 13, 2603–2609, doi:10.3762/bjoc.13.257

• the C9–OH and C17–OH of the aglycone, the protecting groups of two hydroxy groups can be successively removed under different conditions. Compound 6 was hydrolyzed in the presence of HOAc to afford 7, and then the subsequent glycosidation of compound 7 with glycosyl donor 8 yielded compound 9

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

• Mukta Shaw,
• Yogesh Kumar,
• Rima Thakur and
• Amit Kumar

Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236

• -deficient pyridinium salt/thiourea cocatalyzed glycosidation is outlined in Figure 4. It is presumed that at first electron-deficient pyridinium salt 3a undergoes 1,2-addition with the acceptor to produce ammonium salt X. The addition of the thiourea derivative as hydrogen-bonding cocatalyst could activate

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• -glycosylation” by Valverde et al. [54], “remote glycosidation” by Takahashi [55] and “templated oligosaccharide synthesis” by Demchenko [56]. Initially introduced by Kusumoto et al. in 1986 [46], the molecular clamping clearly demonstrated the advantages that intramolecular glycosylations can offer. The first

• attempt to obtain a target disaccharide quipped with muramic acid from donor 1 and acceptor 2 failed (Scheme 2). The authors rationalized that “… a novel device was required to facilitate the coupling. We thus tried to connect the two components prior to the glycosidation reaction with an ester linkage

• close proximity to each other certainly favored the formation of the desired glycoside bond in the above experiment. Thus, this is the first example of the so-called “entropic activation” in glycosidation reaction.” The authors have also projected that the “entropic activation demonstrated in this work

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• of Shreiner’s thiourea as a catalyst in glycosidation with O-glycosyl trichloroacetamides as glycosyl donors [97]. α-D-glucopyranosyl trichloroacetimidate 249 was employed as a donor, several alcohols were utilized, achieving moderate to excellent anomeric selectivity (Scheme 78). Other O-glycosyl

N-Alkyl derivatives of diosgenyl 2-amino-2-deoxy-β-D-glucopyranoside; synthesis and antimicrobial activity

• Agata Walczewska,
• Daria Grzywacz,
• Dorota Bednarczyk,
• Małgorzata Dawgul,
• Andrzej Nowacki,
• Wojciech Kamysz,
• Beata Liberek and
• Henryk Myszka

Beilstein J. Org. Chem. 2015, 11, 869–874, doi:10.3762/bjoc.11.97

• summarized and presented. We have studied different glycosyl donors, different amine group protections, different solvents and promoters to find the best way to obtain 7. The presented compilation is informative for all those interested in the glycosidation of 2-amino-2-deoxy sugars. Results and Discussion

A carbohydrate approach for the formal total synthesis of (−)-aspergillide C

• Pabbaraja Srihari,
• Namballa Hari Krishna,
• Ydhyam Sridhar and
• Ahmed Kamal

Beilstein J. Org. Chem. 2014, 10, 3122–3126, doi:10.3762/bjoc.10.329

• tri-O-acetyl-D-galactal. A C-glycosidation, Trost’s hydrosilylation and protodesilylation protocol have been used as the key steps for achieving the formal total synthesis. Structures of aspergillides. Key NOESY correlations observed in compound 11. Retrosynthetic analysis for (−)-aspergillide C

Efficient carbon-Ferrier rearrangement on glycals mediated by ceric ammonium nitrate: Application to the synthesis of 2-deoxy-2-amino-C-glycoside

• Alafia A. Ansari,
• Y. Suman Reddy and
• Yashwant D. Vankar

Beilstein J. Org. Chem. 2014, 10, 300–306, doi:10.3762/bjoc.10.27

• carried out with several glycals (Table 2). and yielded a single product in all cases studied. In the case of glycals 1a–d, only the α-anomer was obtained as has been reported by Danishefsky et al. in the first report on the C-glycosidation of glycals with allyltrimethylsilane by using TiCl4 [23]. The

Gold-catalyzed glycosidation for the synthesis of trisaccharides by applying the armed–disarmed strategy

• Abhijeet K. Kayastha and
• Srinivas Hotha

Beilstein J. Org. Chem. 2013, 9, 2147–2155, doi:10.3762/bjoc.9.252

• oligosaccharides. The gold catalysis for glycosidation reactions, in which alkynylated glycosides are used, has emerged as one of the versatile options in this regard. A cleavage of the interglycosidic bond that was thought to be due to the higher reaction temperature and the acidic medium was observed during the

• moiety were screened. It was found that 1-ethynylcyclohexanyl (Ech) glycosides are suitable for carrying out the glycosidation at 25 °C in the presence of 5 mol % each of AuCl3 and AgSbF6. Subsequently, Ech-glycosides were observed to be suitable for the synthesis of trisaccharides under gold catalysis

• conditions. Keywords: alkynes; armed–disarmed effect; glycosidation; gold; Introduction Observations that gold(III) has a great affinity for alkynes placed the chemistry of gold in an enviable situation that culminated into the total synthesis of several natural products, in which gold-mediated reactions

Synthesis of 4” manipulated Lewis X trisaccharide analogues

• Christopher J. Moore and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2012, 8, 1134–1143, doi:10.3762/bjoc.8.126

• activation of the anomeric acetate and glycosidation with trichloroethanol; and (3) Zemplén deacetylation. This sequence of reactions gave the desired galactoside 14 in 78% yield and as a 9:1 α/β mixture, as assessed by 1H NMR. It is important to point out that the second step in this sequence of reactions

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• to be entirely consistent with accepted stereoelectronic principles in organic chemistry [45][46][47]. Given these arguments, the obvious question for the alternative stereochemical outcome of the cyclo-glycosidation reaction for the cases n = 3, 4 and 5 (series c, b and a) arises: In terms of the

• aromatic-stacking interactions (ASI). Stereo view of the superposition of β(1→3)-linked disaccharide models of 6a–d in stable triad-ASI conformations. 6a (n = 5) orange, 6b (n = 4) green, 6c (n = 3) pink, 6d (n = 2) magenta. Most-stable product conformations for the cyclo-glycosidation reaction with ring

• than 2.2 kcal/mol with respect to the β(1→3) isomer 6d. Most-stable product conformations for the cyclo-glycosidation reaction with ring size spacer n = 3 (constitutions 6c, 7c, 8c, and further the isomer β(1→2), were not observed). As in Figure 6, the various regio- and stereoisomers were modeled and

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• Glycosidation of 8-azidooctan-1-ol (Supporting Information File 2) using glycosyl bromide 11 [36] in the presence of AgOTf, and debenzoylation of the crude product gave 12 in 81% yield over 2 steps (Scheme 2). Regioselective silylation of the primary alcohol of 12 with TPSCl followed by benzoylation of the

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• thioglycoside 4 [14] yielded the 6-O-silylated compound 5 (92%), benzylation of which gave donor 6 (85%). A benzyl group in the 4-position was preferred to an ester group to avoid the risk of acyl migration during subsequent reactions; desilylation, glycosidation and phosphorylation. 3II,4II-Diols of lactose

• from 7, Scheme 2). NIS/AgOTf-promoted glycosidation of this acceptor with donor 10 [19] (1.4 equiv) then efficiently gave the β-linked trisaccharide 11 (83%). At this stage the phthalimido group was removed by aminolysis and the resulting amino compound acetylated to yield 12 (93%) with the target

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• enantioenriched sordaricin proceeded in a like fashion. Finally, (−)-sordarin was reached starting with glycosidation of sordaricin ethyl ester 55 with fluoride 56. This step relied on a Mukaiyama diastereoselective glycosidation [34], wherein the p-methoxybenzoyl group provides 1,3-anchimeric assistance during

Study of thioglycosylation in ionic liquids

• Jianguo Zhang and
• Arthur Ragauskas

Beilstein J. Org. Chem. 2006, 2, No. 12, doi:10.1186/1860-5397-2-12

• . reported that the glycosidations of glucopyranosyl fluorides with assorted alcohols employing an ionic liquid and a protic acid catalyst proceeded, under mild conditions, to afford the corresponding glycosides in 54–91% yields.[7] The stereoselectivity of the glycosidation was significantly affected by the

• -butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium methyl sulfate were also explored as glycosidation solvents, under the same reaction conditions. These thioglycosylation reactions in these solvents were found to be either unsuccessful or provided significantly reduced

• glycosyl donors. Glycosylation of 1 and 2 with various alcohols in [bmim]BF4 with methyl triflate. Glycosidation of 1 and benzyl alcohol in [bmim]BF4 with methyl triflate and water. a-c. The percentage of hydrolyzed methyl trifluoromethanesulfonate in DMSO, CDCl3, and [bmim]BF4. Supporting Information