A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups

• Naser-Abdul Yousefi,
• Morten L. Zimmermann and
• Mikael Bols

Beilstein J. Org. Chem. 2022, 18, 1553–1559, doi:10.3762/bjoc.18.165

• are deprotected more readily than the secondary alcohols of 1. Results and Discussion The starting point of the synthesis is the known partially benzylated derivative 6, which according to the literature can be made either from 2 by selective acetolysis of all the primary benzyl groups and ester

• cleavage [16] or from 1 by selective protection of the primary OH groups with tert-butyldimethylsilyl groups, followed by benzylation and desilylation [17][18]. We used both methods to prepare 6: The acetolysis method is convenient when perbenzyl α-cyclodextrin (2) is at hand but requires very strict

• temperature control during the acetolysis step. The silylation method requires careful drying of 1 before the silylation but is otherwise experimentally simple. Hexol 6 was then DCB-protected using 2,4-dichlorobenzyl chloride and sodium hydride in DMSO. As self-condensation of the alkylating agent is possible

Chemical and chemoenzymatic routes to bridged homoarabinofuranosylpyrimidines: Bicyclic AZT analogues

• Sandeep Kumar,
• Jyotirmoy Maity,
• Banty Kumar,
• Sumit Kumar and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2022, 18, 95–101, doi:10.3762/bjoc.18.10

• ]. Azidofuranoside 11 on acetolysis with acetic acid/acetic anhydride/sulfuric acid (100:10:0.1) at room temperature afforded an anomeric mixture of 1,2,5,6-tetra-O-acetyl-3-azido-3-deoxy-α,β-ᴅ-allofuranose (12a,b), which on Vorbrüggen base coupling [29] with thymine and uracil in the presence of N,O-bis

• regioselective protection of the primary hydroxy group of diol 17 using TBDPS-Cl in pyridine at room temperature afforded TBDPS-protected furanoside 18, which on acetolysis using AcOH/Ac2O/H2SO4 (100:10:0.1) afforded the anomeric mixture of coupling sugar 19a,b in 80% yield. The Vorbrüggen coupling [29] of

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• COS, which requires tedious purification steps. Furthermore, degradation of natural chitin often lacks proper control over the pattern of acetylation (PA). Acetolysis also often leads to heterogeneous mixtures [232][233][234][235]. A controlled acetolysis of chitin, followed by the one-pot trans-N

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• bond is opposite to the fluorinated fragment (the distal bond) [2]. The ring-opening reactions of (2,2-difluorocyclopropyl)methyl systems: Dolbier investigated the acetolysis of tosylates 104 and 105 (Scheme 48) [96]. The difference between compounds 104 and 105 is the presence of a methyl substituent

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• diacetate 18 under acetolysis conditions (Ac2O/BF3∙OEt2) [22]. However, besides the expected diacetate 18, 1,2,6-tri-O-acetate 19 was observed and isolated as a byproduct (Scheme 4). The cleavage of the O-benzyl ethers followed by acetylation of the liberated hydroxy groups under acidic conditions was

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

• in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysis products were obtained in moderate yields under tin(IV) chloride catalysis. Our methodology could be extended to regioselective protecting group installations and manipulations towards a number of

• thiosialoside and halide donors. Keywords: acetolysis; acetolysis products; 2,7-anhydrosialic acid; SnCl4; Introduction Sialic acids are the most prevalent monosaccharides that are found at the nonreducing ends of glycans, and they are involved in many biologically important ligand–receptor interactions [1

• -anhydro bridges [29][30][31]. Accordingly, ᴅ-galactosamine and ᴅ‑allosamine derivatives were synthesized via scandium(III) triflate-catalyzed ring opening of 1,6-anhydroglucosamine derivatives [29][32]. However, there is a paucity of reports on the Lewis acid-catalyzed acetolysis of the 2,7-anhydro

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• ]. The similarity of products formed from acetolysis of 32 and 42 implies that the same cation rearrangement manifold is involved. Scheme 9 gives a mechanistic rationale for these products. Capture of an unrearranged discrete cyclopropylcarbinyl cation 43 gives the major product 38, while migration of

• cyclopropylcarbinyl alcohol, which was available from methyl 2-diazopropanoate by a process completely analogous to the synthesis of the phenyl analog 17. The mesylate derivative was too reactive for rates to be measured and hence the trifluoroacetate derivative 48 was studied. Acetolysis gave the acetate 50 along

• ) gives methylcyclobutene (51) (68%) as the major acetolysis product, along with minor products that are identical to those previously reported [52] in solvolysis of the trifluoroacetate derivative of (1r,3r)-1-methyl-3-(trimethylsilyl)cyclobutanol. As in the case of mesylate 32, the γ-trimethylsilyl

An efficient synthesis of a C₁₂-higher sugar aminoalditol

• Łukasz Szyszka,
• Anna Osuch-Kwiatkowska,
• Mykhaylo A. Potopnyk and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2017, 13, 2146–2152, doi:10.3762/bjoc.13.213

• was the liberation of the anomeric position (C1), which, as we noticed, can cause problems. We subjected azide 4 to acetolysis and, although this reaction is very capricious in higher sugar chemistry [7][8], succeeded in the preparation of the desired hemiacetal acetate 5 in very good yield (86%) as a

• ; Anal. calcd for C76H79N3O11: C, 75.41; H, 6.58; N, 3.47; found: C, 75.41; H, 6.47; N, 3.34. Acetolysis of glycoside 4; synthesis of 5 Azide 4 (0.36 g, 0.3 mmol) was dissolved in ethyl acetate (2.3 mL) to which acetic anhydride (4.6 mL) and sulfuric acid (0.72 mL of the solution: conc. H2SO4 (0.05 mL

Enzymatic separation of epimeric 4-C-hydroxymethylated furanosugars: Synthesis of bicyclic nucleosides

• Neha Rana,
• Manish Kumar,
• Vinod Khatri,
• Jyotirmoy Maity and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2017, 13, 2078–2086, doi:10.3762/bjoc.13.205

• ) in 98% yield. The glycosyl donor 7a,b was prepared from acetolysis of compound 6 with acetic acid/acetic anhydride/sulfuric acid (100:10:0.1) in 93% yield. The Vorbrüggen coupling [17] of 7a,b with uracil in the presence of N,O-bis(trimethylsilyl)acetamide (BSA) and trimethylsilyltrifluoromethane

• product 4b in 95% yield. Thus, the acetylation of the lone hydroxy group of 10 using acetic anhydride and DMAP in dichloromethane afforded 3,5-di-O-acetyl-1,2-O-isopropylidene-4-C-p-toluenesulfonyloxymethyl-α-D-xylofuranose (11) in 98% yield. Acetolysis of compound 11 yielded the glycosyl donor 12a,b in

• procedure for the acetolysis of compounds 6 and 11: synthesis of tetraacetate compounds 7a,b and 12a,b. Similar as described in [18] acetic anhydride (6.2 mL, 65.43 mmol) and concentrated sulfuric acid (0.03 mL, 0.65 mmol) was added to a stirred solution of compound 6 (3 g, 6.5 mmol) in acetic acid (37.4 mL

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• oxazoline formation, the order of reactions was reversed, and triethylsilyl triflate (TESOTf)-catalyzed [58] acetolysis of the 1,6-anhydro bridge in 19 gave 42 (Table 1) as a mixture of anomers from which the α-anomer crystallized. TESOTf as a catalyst for acetolysis gave better results than sulfuric acid

• , TESOTf-catalyzed acetolysis and subsequent hydrogenation (Pd/C in a mixture of ethanol and acetic anhydride) was applied to obtain the target acetylated fluoro analogs (Table 1). Compound 21 was acetolyzed to 43 which was obtained as a mixture of anomers and characterized by NMR and finally hydrogenated

• to furnish acetylated 3-fluoro-GalNAc 6 isolated as a separable mixture of anomers. The D-galacto configuration of 6 is manifested by the lower 3JH3,H4 coupling value (3.4 Hz, α-anomer) in comparison with that of its C-4 epimer 5 (8.6 Hz, α-anomer). Acetolysis of the internal acetal in 26 proceeded

Expedient synthesis of 1,6-anhydro-α-D-galactofuranose, a useful intermediate for glycobiological tools

• Luciana Baldoni and
• Carla Marino

Beilstein J. Org. Chem. 2014, 10, 1651–1656, doi:10.3762/bjoc.10.172

• differentially protected hydroxy groups at position 1 and 6, for example the diacetyl derivative 6 obtained by the acetolysis of 5 (Scheme 1) [16]. In this way, compound 5 would give access to donors in which the 6-position could subsequently be manipulated for the construction of a 1→6 linkage. Based on this

Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica

• Lu Zou,
• Ruixiang Blake Zheng and
• Todd L. Lowary

Beilstein J. Org. Chem. 2012, 8, 1219–1226, doi:10.3762/bjoc.8.136

• affording 15. The benzylidene protecting group was cleaved, together with the methyl glycoside, by acetolysis giving the tetra-O-acetylated compound 16 in 81% yield. This glycosyl acetate was converted to the corresponding thioglycoside (17), which was, in turn, coupled with dibenzyl phosphate under NIS

• % yield. Acetolysis of 27 to the corresponding glycosyl acetate 28, followed by reaction with ethanethiol and BF3·OEt2, yielded thioglycoside 29, in a modest 39% yield from 27 over two steps. This compound was then converted to 11, in 56% yield, as outlined above, by successive phosphorylation and

• . Acetolysis conditions were used to replace the methyl group at the anomeric center in 38 with an acetyl group, resulting in a 96% yield of 39. Thioglycosylation, followed by coupling of the resulting thioglycoside donor 40 (obtained in 75% yield) with dibenzyl phosphate, gave phosphate 41 in a yield of 67

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

• and H2 [40]. Unambiguous stereochemical assignment of (7S)-18 was achieved by single crystal X-ray analysis as shown in Figure 3, and is consistent with stereoselective delivery of hydride to the exo-face of the intermediate dioxolenium ion. Acetolysis of the benzylidene acetal 18 using 2% H2SO4/Ac2O