Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• ]. The ratio of α/β-anomers in compound 5 was found to be influenced by the reaction conditions, consistently favoring the β-anomer. Further transformation of compound 5 involved α-selective phosphite formation using dibenzyl N,N-diisopropylphosphoramidite and 5-(ethylthio)-1H-tetrazole. The resulting α

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• trifluoroacetyl group at O-9 was more α-selective (23% difference) while at high concentration (0.15 mol·L−1) sialyl donor 2 with a chloroacetyl group at O-9 was more α-selective (50% difference) and the relative difference in stereoselectivity increased at high concentration (0.15 mol·L−1). Importantly, clear

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• corresponds to the observed major isomer product (Figure 15). In a related transformation, Hong realized the exclusively α-selective hydroacylation of ynones, ynoates, and ynamides via photoredox nickel catalysis. Thus, the combination of nickel and iridium catalysts efficiently catalyzed the regioselective α

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• compound 12. Due to the absence of a hydrogen bond, azido-protected glycal 13 could be used as acceptor for reactions at its OH-4 and OH-8 group [36][37]. Moreover, it was used as sialyl donor in α-selective glycosylation reactions [35]. Next, acetolysis of 2,7-anhydro derivative 6 was examined with SnCl4

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• uronic acid in an α-selective fashion. A variety of azido hemiacetal glucoside donor and uronic acid thioglycosyl acceptor pairs were screened under preactivation conditions. The anomeric leaving groups of the acceptors had significant impacts on the glycosylation outcomes (Scheme 11a). When donor 54 was

Versatile synthesis of the signaling peptide glorin

• Robert Barnett,
• Daniel Raszkowski,
• Thomas Winckler and
• Pierre Stallforth

Beilstein J. Org. Chem. 2017, 13, 247–250, doi:10.3762/bjoc.13.27

• challenge in the syntheses of glorin and analogs is the differentiation between the α- and the γ-carboxylic acid groups of L-glutamic acid for selective esterification or amidation. α-Selective functionalization was achieved via synthesis of oxazolidinone 6 from Cbz-L-glutamic acid (5) with paraformaldehyde

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

• Mikael Bols and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2017, 13, 93–105, doi:10.3762/bjoc.13.12

• the bulky C4 substituent shields the β-face of the donor and hence the glycosylation is very α-selective. The remarkable difference in reactivity between disarmed, armed and superarmed donors 20, 26 and 32, respectively was used for “one-pot one addition” glycosylations having all 3 donors present

• ]. This, together with the results with the α-selective TBS-protected mannosyl and galactosyl donors (Table 1) [24], shows that there is no general trend with respect to the selectivity of these donors. On the other hand, the configurationally inverted fully TBS-protected phenyl thiorhamnoside was found

• to be highly α-selective (Table 1) presumably due to steric hindrance from the 2-O-TBS on the β-face. This donor was recently used in the synthesis of glycosyltransferase acceptor substrates [53]. Yet the 2-O-TBS protection does not always have this effect. In a recent paper it was shown that in a

TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals

• Mei-Yuan Hsu,
• Yi-Pei Liu,
• Sarah Lam,
• Su-Ching Lin and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2016, 12, 1758–1764, doi:10.3762/bjoc.12.164

• 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. Keywords: 2-deoxyglycosides; glycals; trimethylsilyl bromide (TMSBr); triphenylphosphine oxide (TPPO

• because of their high stability and reactivity [43]. Numerous stereoselective synthetic methods that use 2-deoxythioglycosides have been reported [9][10][44][45][46][47][48][49]. We recently developed a glycosyl chloride-mediated synthesis of highly α-selective 2-deoxyglucosides by using 2

• - and α-selective O-2-deoxyglycosides from glycals. Results and Discussion In our preliminary study, 77% yield of 2-deoxythiolglucoside 2 was produced exclusively when glucal 1 in the presence of p-thiocresol was promoted by a stoichiometric amount of TMSBr under neat conditions at room temperature

(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

• employed as the catalyst (Scheme 76) [95]. Product 243 was obtained in high yield (85%), high ee values (up to 99%) and high diastereoselectivity (8.1:1). In 2012, an interesting α-selective approach for the synthesis of galactopyranoses using achiral thiourea organocatalyst 20, was reported from

A general metal-free approach for the stereoselective synthesis of C-glycals from unactivated alkynes

• Shekaraiah Devari,
• Manjeet Kumar,
• Ramesh Deshidi,
• Masood Rizvi and
• Bhahwal Ali Shah

Beilstein J. Org. Chem. 2014, 10, 2649–2653, doi:10.3762/bjoc.10.277

• single step from a variety of acetylenes , i.e., arylacetylenes and most importantly aliphatic alkynes. Keywords: α-selective; C-alkynylation; glycal; metal free; TMSOTf; Introduction C-Glycosides represent an important class of carbohydrate mimics, owing to their presence in a large number of

• groups, while the stereoelectronic control allows the α-pseudo-axial orbital to form the bond [35]. Conclusion In conclusion, we developed a highly efficient and α-selective method for the synthesis of alkynyl glycosides from virtually any alkyne, that is, aliphatic and aromatic. To the best of our

Design and synthesis of multivalent neoglycoconjugates by click conjugations

• Feiqing Ding,
• Li Ji,
• Ronny William,
• Hua Chai and
• Xue-Wei Liu

Beilstein J. Org. Chem. 2014, 10, 1325–1332, doi:10.3762/bjoc.10.134

• -allohexopyranoside (2a) in gram scale via BF3∙OEt2-promoted one-pot three-component α-selective tandem hydroamination/glycosylation reaction (Scheme 1). In fact, when 3,4,6-tri-O-acetyl-D-glucal (1a), propargyl alcohol and p-toluenesulfonamide were subjected to a one-pot reaction in the presence of 2.2 equiv of BF3

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• compound 4a (60–70%) and bromide 5a (30–40%). In 5a, the oxirane ring was opened by nucleophilic Br− ions produced by Ph3P and CBr4. Also in the DMF-promoted reaction, a mixture of 4a (70–90%) and 5a (10–30%) was derived. In both reaction pathways, however, the glycosylation was α-selective (α:β ≥ 90:10