Synthesis of monophosphorylated lipid A precursors using 2-naphthylmethyl ether as a protecting group

• Jundi Xue,
• Ziyi Han,
• Gen Li,
• Khalisha A. Emmanuel,
• Cynthia L. McManus,
• Qiang Sui,
• Dongmian Ge,
• Qi Gao and
• Li Cai

Beilstein J. Org. Chem. 2020, 16, 1955–1962, doi:10.3762/bjoc.16.162

• ) group under basic conditions followed by peracetylation afforded compound 10 on a ≈150 g scale. The regioselective anomeric deacetylation with hydrazine and reprotection of the anomeric hydroxy group as tert-butyldimethylsilyl ether (TBS) led to compound 12. Compound 12 was then treated with sodium

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• constant k2 of ManNCyoc has previously been reported to be k2 = 0.99 M−1s−1 [24]. To determine k2 of Cyc- and Cp-modified mannosamine, we synthesized ManNCyc and ManNCp according to published protocols [23][27], omitting the final peracetylation step. In this way, water-soluble compounds were obtained that

• , mannosamine hydrochloride (ManN·HCl) was neutralized with Hünig’s base (diisopropylethylamine, DIPEA) in DMF and reacted with the activated cyclopropene derivatives, followed by peracetylation with acetic anhydride in pyridine. Ac4ManNCp(H2) could be obtained in 34% yield and Ac4ManNCyc(H2) in 52% yield

• Ac4GlcNCp might be better incorporated than Ac4GlcNCyoc. Consequently, we synthesized Ac4GlcNCp and Ac4GalNCp (Scheme 4). Glucosamine hydrochloride and galactosamine hydrochloride, respectively, were neutralized with sodium methoxide and then reacted with activated cyclopropene 6 followed by peracetylation

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

• interconversions, and peracetylation were followed by conversion to the oxazoline, using TMSBr, BF3·Et2O and collidine, and finally deacetylation. It was found that the incorporated azide was tolerated by the ENGase enzyme (Endo A), and so a modified glycoprotein (RNase) was made by enzymatic attachment of this

Diosgenyl 2-amino-2-deoxy-β-D-galactopyranoside: synthesis, derivatives and antimicrobial activity

• Henryk Myszka,
• Patrycja Sokołowska,
• Agnieszka Cieślińska,
• Andrzej Nowacki,
• Maciej Jaśkiewicz,
• Wojciech Kamysz and
• Beata Liberek

Beilstein J. Org. Chem. 2017, 13, 2310–2315, doi:10.3762/bjoc.13.227

• -β-D-galactopyranoside (4) (Scheme 1). This glycosyl donor was N-protected with the tetrachlorophthaloyl (TCP) group. The synthesis of 4 started from commercially available D-galactosamine hydrochloride which was first converted to the 2-N-tetrachlorophthaloyl derivative followed by peracetylation

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

• ]. However, chemical complementation with mycolactone restored the typical M. ulcerans pathology for mycolactone-deficient strains [35]. Some chemical modifications were performed on the purified extracts showing that peracetylation or exhaustive double bond saturation by hydrogenation resulted in a total

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• after in situ peracetylation (Table 2, entry 8). The scope of the TBAB-catalyzed silyl protection under solvent-free conditions was next examined for the regioselective attachment of TBDPS (Table 2, entries 9–13), a commonly used silyl protecting group bulkier than TBDMS and more resistant to acidic

Tunable microwave-assisted method for the solvent-free and catalyst-free peracetylation of natural products

• Manuela Oliverio,
• Paola Costanzo,
• Monica Nardi,
• Carla Calandruccio,
• Raffaele Salerno and
• Antonio Procopio

Beilstein J. Org. Chem. 2016, 12, 2222–2233, doi:10.3762/bjoc.12.214

• Catanzaro, Viale Europa, Loc. Germaneto, 88100 Catanzaro, Italy Department of Chemistry, Università della Calabria, Cubo 12C, 87036-Arcavacata di Rende (CS), Italy 10.3762/bjoc.12.214 Abstract Background: The peracetylation is a simple chemical modification that can be used to enhance the bioavailability

• of hydrophilic products and to obtain safe and stable pro-drugs. Results: A totally green, solvent-free and catalyst-free microwave (MW)-assisted method for peracetylation of natural products such as oleuropein, alpha-hederin, quercetin and rutin is presented. By simply tuning the MW heating program

• green acetylation of hydrophilic biological molecules, potentially easily scalable for industrial applications, including pharmaceutical, cosmetic and food industry. Keywords: catalyst-free; microwaves; peracetylation; polyhydroxylated compounds; solvent-free; Introduction Peracetylation of alcohols

Diastereoselective synthesis of new O-alkylated and C-branched inositols and their corresponding fluoro analogues

• Charlotte Collet,
• Françoise Chrétien,
• Yves Chapleur and
• Sandrine Lamandé-Langle

Beilstein J. Org. Chem. 2016, 12, 353–361, doi:10.3762/bjoc.12.39

• chloride, followed by peracetylation with acetic anhydride in a one pot reaction [46]. Myo-18 and scyllo-18 were obtained in 74 and 70% yield, respectively. It is worthy to note that the tertiary hydroxy group in myo-18 and scyllo-18 remained unprotected under these conditions. The literature data are

• peracetylation with acetic anhydride in one pot was carried out [46]. Compounds myo-26 and scyllo-26 were obtained in 67% and 70% yields, respectively. However, as already observed for the two carbon-atoms-arm-branched compounds, the tertiary hydroxy group remained unprotected. As explained above, the protection

Synthesis, antimicrobial and cytotoxicity evaluation of new cholesterol congeners

• Mohamed Ramadan El Sayed Aly,
• Hosam Ali Saad and
• Shams Hashim Abdel-Hafez

Beilstein J. Org. Chem. 2015, 11, 1922–1932, doi:10.3762/bjoc.11.208

• as a proof of structure. Substitution of the DMM group with an acetyl group was performed under standard conditions, i.e., treatment with NaOH for ring opening [39], HCl at pH 5 for amide cleavage, peracetylation and then O-deacetylation. Under these conditions, compound 17 was prepared in 37% yield

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• amide bond and evaluated their efficacy as modulators for β-lactam resistance in S. aureus. Landis-Piwowar et al. [68] and Wang et al. [69] protected the hydroxy groups through peracetylation. These analogs behave as prodrugs and the acetyl group is removed by cellular cytosolic esterases. Liao et al

Indium-mediated allylation in carbohydrate synthesis: A short and efficient approach towards higher 2-acetamido-2-deoxy sugars

• Christopher Albler,
• Ralph Hollaus,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2014, 10, 2230–2234, doi:10.3762/bjoc.10.231

• obtained allylic epoxides were regio- and stereoselectively opened with trimethylsilyl azide under palladium catalysis. Finally, a suitable deprotection protocol, starting with acidic acetate cleavage and ozonolysis was established. Peracetylation of the products simplifies purification and subsequent

A promising cellulose-based polyzwitterion with pH-sensitive charges

• Thomas Elschner and
• Thomas Heinze

Beilstein J. Org. Chem. 2014, 10, 1549–1556, doi:10.3762/bjoc.10.159

• Europe and were used without further treatment. Cellulose phenyl carbonate was prepared by esterification of cellulose, dissolved in N,N-dimethylacetamide (DMAc)/LiCl, applying pyridine and phenyl chloroformate [21]. 1, DS 1.92 (determined by means of 1H NMR spectroscopy after peracetylation), FTIR (KBr

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• set the stage for mesylation, and conversion of 3 to fluoride 4 with an extremely economical reagent. Acetal cleavage and peracetylation released glycoside 5 which was converted to 6 via known methods. The main disadvantages of the approach are the extensive use which must be made of protection

De novo synthesis of D- and L-fucosamine containing disaccharides

• Daniele Leonori and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 332–341, doi:10.3762/bjoc.9.38

• standard Upjohn conditions gave, after peracetylation with Ac2O, D-fucosamine building block D-8a in 81% yield and 5:1 dr (anti/syn, diastereomers separable by column chromatography) (Scheme 3) [60][61][62]. The formation of the desired C3–C4–C5 syn,syn cyclic product was confirmed based on observation of

• a 3JH3–H4 coupling of 3.5 Hz. When the same sequence of dihydroxylation–peracetylation was performed on Bz-substituted aldehyde 6b, compound D-8b was formed in 71% as a single diastereomer (Scheme 3). This product was crystallized from n-hexane/EtOAc solvent mixture, and the stereochemical

• (four steps, two chromatographic purifications) that after the direct oxidation–dihydroxylation–peracetylation protocol yielded the desired L-fucosamine building block L-8a (Scheme 5). Synthesis of fucosamine-containing disaccharides To facilitate the use of the bacterial monosaccharides in the glycan

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

• ) giving acceptor 8 in 62% yield. The syntheses of trichloroacetimidate donors 9–11 are described on Scheme 1; they were all prepared from the known trichloroethyl galactoside 14 [57]. Galactoside 14 was first prepared in three steps from galactose: (1) peracetylation (Ac2O-pyridine); (2) BF3·OEt2

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• with Pd/C [36], followed by a Zemplén saponification to obtain product 15. Starting from 4′,6′-O-benzylidene maltose 10 [37], the primary alcohol was protected as tert-butyldimethylsilyl ether followed by standard peracetylation (Scheme 2). Treatment of the silyl protecting group with an excess of

Cross-metathesis of allylcarboranes with O-allylcyclodextrins

• Ivan Šnajdr,
• Zbyněk Janoušek,
• Jindřich Jindřich and
• Martin Kotora

Beilstein J. Org. Chem. 2010, 6, 1099–1105, doi:10.3762/bjoc.6.126

• peracetylation [7][24]. At the outset cross-metathesis of allylcarborane 1a with 2I-O-allylcyclodextrin 2a and various ruthenium-carbene complexes (10 mol %) in dichloromethane was carried out to assess the most suitable catalyst (for cross-metatheses involving carboranes, see: [25][26]). However, when the

Preparation of aminoethyl glycosides for glycoconjugation

• Robert Šardzík,
• Gavin T. Noble,
• Martin J. Weissenborn,
• Andrew Martin,
• Simon J. Webb and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2010, 6, 699–703, doi:10.3762/bjoc.6.81

• 2-chloroethanol under acid catalysis, followed by peracetylation, nucleophilic substitution with azide and finally, reduction of the azido group [13][14]. Alternatively, the carbohydrate was first activated as the trichloroacetimidate or bromide followed by glycosylation with N-Cbz-aminoethanol [15

Chemical synthesis using enzymatically generated building units for construction of the human milk pentasaccharides sialyllacto-N-tetraose and sialyllacto-N-neotetraose epimer

• Dirk Schmidt and
• Joachim Thiem

Beilstein J. Org. Chem. 2010, 6, No. 18, doi:10.3762/bjoc.6.18

• the donor building block. For formation of the disaccharide acceptor 6, a straight-forward three-step standard reaction sequence was used [10]. Methyl β-lactoside was isopropylidenated at 3′,4′-position with dimethoxypropane and p-toluene sulfonic acid in DMF/acetone. Peracetylation (Ac2O/Py) and

• side products and separated by chromatography but these were not further characterized. Reduction of the 2′′′-azido to the 2′′′-amino group with nickel boride [12][13] followed by peracetylation gave 8 in 81% yield (Scheme 1). 1H NMR spectrum contained a doublet for H-1″ at δ 4.96 (J1″2″ = 8.0 Hz) and

• 32% by transsialylation with recombinant transsialidase (Trypanosama cruzi) [8]. Formation of the methyl ester and peracetylation led to the trisaccharide donor building block 10. Synthesis of the disaccharide acceptor in this case started from methyl β-lactoside, which was transformed into its 4′,6

Methods for the synthesis of polyhydroxylated piperidines by diastereoselective dihydroxylation: Exploitation in the two-directional synthesis of aza-C-linked disaccharide derivatives

• Andrew Kennedy,
• Adam Nelson and
• Alexis Perry

Beilstein J. Org. Chem. 2005, 1, No. 2, doi:10.1186/1860-5397-1-2

• , after peracetylation of the crude product, dihydroxylation of the remaining alkene of 24 under Donohoe's reaction conditions was not possible. The dihydroxylation reactions performed using Donohoe's reaction conditions were, to some extent, complementary (for example, compare entry 1a with 1b, and entry

• 2a with 2b, Table 1). With the syn allylic alcohol 17, dihydroxylation was highly (>95:<5) syn selective, yielding the triacetate 20B in 70% yield after peracetylation (entry 1b, Table 1). We have previously observed that the pseudo-equatorial allylic hydroxyl groups of similar dihydropyrans had been

• the alcohols in the bis-allylic alcohol substrate trans-33: selective inversion of the piperidin-3-ol was possible (91:9 selectivity between the alcohols). Two-directional dihydroxylation, and peracetylation, yielded the aza-C-linked disaccharide derivatives (Scheme 8); the yields of products (Scheme