N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• product can be explained by rearrangement of the rhamnosyl group from the oxygen to the nitrogen atom. Oxidative debenzylation of 5a afforded 5b in high yield. Unfortunately, all attempts to remove the pivaloyl protective groups failed. On the other hand, employment of tri-O-acetyl-α-ʟ-rhamnosyl

• debenzylation of 7a gave product 7b which was transformed to the desired product 7c by reaction with sodium methoxide and subsequent treatment with acidic ion exchange resin Amberlyst 15. The synthesis of akashins A–C was studied next. This required the synthesis of the corresponding indigo and carbohydrate

• -glycoside 11a (Scheme 7) [20]. Debenzylation gave product 11b which was transformed to akashin A (11c) by reduction of the azide to the amine in the presence of propane-1,3-dithiol and subsequent debenzoylation. Akashin A was transformed to akashins B and C by acetylation and reaction with diacetyl

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• . The oxetane compound 6 was further derivatized to incorporate a pyrrolidine moiety in presence of ammonia. Upon debenzylation at C-3, the target compound 7 was obtained in an 18% overall yield from 3. The pyrrolidino-oxetane derivative exhibited potent inhibition of Hedgehog signaling, comparable to

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• full conversion of 2a under the standard reactions, 1.0 equiv of each substrate was added synchronously. After running 5 times, 65% yield was obtained within a total reaction time of 60 h. Finally, we explored the synthetic versatility of the products in this methodology. Debenzylation of product 4aa

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• the alcoholate reacted with 1-iodohexadecane to produce 3.3 in 50% yield. The phosphocholine moiety was incorporated by using 2-bromoethyl dichlorophosphate as a key reagent and following a previously reported sequence [67]. The debenzylation by using hydrogenolysis conditions produced 3.5 in 75% to

• benzylation produced 4.13. Then, the deprotection of the primary alcohol in acidic conditions allows introducing the phosphocholine polar head group by using POCl3 and the choline tosylate salt as reagents to yield 4.14. Finally, the debenzylation of the secondary alcohol and its acylation produce PAF 4.15. b

• ) The second scheme is shorter (Figure 4D) and starts with the acylation of 4.16 to produce 4.17. Then, the debenzylation of the primary alcohol produced 4.18. Interestingly, the migration of the acetyl group from sn-2 to sn-3 position was not observed. Finally, the installation of the phosphocholine

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• after recrystallization. Subsequent ozonolysis of the terminal alkene functionality with a follow-up reduction furnished primary alcohol 134 which was transformed into the azide 135. Reduction of the azide 135 was accompanied by debenzylation, was followed by tosylation of the primary amine and exchange

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• (II)–alkenyl intermediate 88. Then, the intermediate 88 undergoes protio-depalladation and demethylation to yield the Z-isomer 85 (Scheme 17b). In case of N-benzylpyridinium salts 83, first debenzylation occurs to form 2-pyridyl–Cu(I) species 89 in the presence of CuBr which then coordinates to the Pd

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

• secondary alcohols was prepared and subjected to DIBAL (diisobutylaluminum hydride)-promoted selective debenzylation. Debenzylation proceeded by first removing two dichlorobenzyl groups from the 6A,D positions and then removing one or two benzyl groups from the 3A,D positions. Keywords: aluminum hydrides

• ; cyclodextrin; debenzylation; 2,4-dichlorobenzyl; selective; Introduction α-Cyclodextrin (1) is a cyclic carbohydrate consisting of six α-1,4-linked ᴅ-glucose molecules (Figure 1). It has a donut-like structure with the glucose residues all aligned with the α-side towards the center of the ring and the polar

• linkers, lids or catalytic groups can be installed which is no simple task due to the many similar functionalities in 1 [5][6][7]. A very useful way to access the hydroxy groups in a selective manner is the perbenzylation of 1 and the subsequent selective debenzylation of 2 using DIBAL [8][9][10]. This

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

• Emine Salamci and
• Ayse Kilic Lafzi

Beilstein J. Org. Chem. 2022, 18, 1539–1543, doi:10.3762/bjoc.18.163

• )cyclooctane-1,2-diyl dimethanesulfonate. Reaction of the bis(benzyloxy)cyclooctane-1,2-diyl dimethanesulfonate with NaN3 gave 2-azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate. Reduction of the azide group and debenzylation to give an amine provided the new 3-aminocyclooctanetriol. Treatment of the 2

• -azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate with Zn/NH4Cl and debenzylation resulted in the target aziridinecyclooctanediol. Keywords: aminocyclitols; aminocyclooctanetriol; azides; aziridines; aziridinecyclooctanediol; Introduction Aziridines are the smallest nitrogen-containing heterocycles

Modular synthesis of 2-furyl carbinols from 3-benzyldimethylsilylfurfural platforms relying on oxygen-assisted C–Si bond functionalization

• Sebastien Curpanen,
• Per Reichert,
• Gabriele Lupidi,
• Giovanni Poli,
• Julie Oble and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2022, 18, 1256–1263, doi:10.3762/bjoc.18.131

• debenzylation/cyclization of benzyldimethysilyl-substituted allylic alcohols [32]. To that end, carbinol 4c was treated with TBAF⋅3H2O (1.0 equiv), which resulted in the formation of 16 in 86% yield (along with toluene, Scheme 6). Alike 5-membered cyclic dimethyl(alkenyl)siloxanes, 16 was found to be highly

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• [2,3-d][1]benzazepin-6(5H)-one (3a). This procedure delivered analytically pure 3a in 80% yield as also confirmed by SC-XRD (Figure 3). The final step to structure C required removal of the benzyl group. Debenzylation of amines is commonly performed by palladium-catalyzed hydrogenation [40]. However

• the lactam ring of 3a. Gratifyingly, we obtained scaffold C in 71% yield by refluxing 3a with aluminum chloride in benzene (Scheme 6) [43]. For comparison, debenzylation of paullone with sodium in liquid ammonia gave A in 40% yield [23]. In addition, the generality of synthetic pathway (c) (Scheme 1

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

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

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• could be performed only with AlCl3 under harsh conditions and, therefore, cannot be used for the preparation of compounds with acid-sensitive substituents. In addition, the debenzylation of 1-benzyl-3-arylpyrido[2,1-a]pyrrolo[3,2-c]isoquinolines A was found to accompany by isomerization to 2-aryl

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• ] synthesized the double-headed nucleoside (1S,3R,4R,6R,7S)-7-hydroxy-1-(hydroxymethyl)-3-(thymin-1-yl)-6-(4-(thymin-1-ylmethyl)-1,2,3-triazol-1-yl)methyl-2,5-dioxabicyclo[2.2.1]heptane (127). The CuAAc reaction of nucleoside azide 126 with propargylated thymine followed by Pd-catalyzed debenzylation under

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• -catalyzed hydrogenolysis in ethanol/acetic anhydride appeared to be a logical deprotection step [26], the desired fluoro sugars were contaminated with varying quantities of unidentified byproducts. However, clean debenzylation was achieved by first converting the azide to an acetamide on reaction with

• degree upon reaction with AcSH in pyridine and traces of O1 acetates were removed by chromatography or recrystallization. Palladium-catalyzed hydrogenolytic debenzylation of 49–58 then yielded the target fluoro analogs 61–70. To complete the series of fluorinated analogs for the purpose of comparing

• conversion and debenzylation. The values [Hz] of selected coupling constants. Boldfaced values illustrate the trends discussed in the text. Supporting Information Supporting Information File 89: Experimental procedures and spectral data. Supporting Information File 90: Copies of 1H, 13C, 19F, and 2D NMR

Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration–oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles

• Lívia Dikošová,
• Júlia Laceková,
• Ondrej Záborský and
• Róbert Fischer

Beilstein J. Org. Chem. 2020, 16, 1313–1319, doi:10.3762/bjoc.16.112

• (Scheme 4). According to the literature, the N-debenzylation by a Pd-catalyzed hydrogenolysis in methanol with formic acid as the hydrogen source [37][38] should allow the access to N-deprotected isoxazolidines. Unfortunately, all attempts to remove the benzyl group directly from the model isoxazolidine

• 8b resulted only in a reductive cleavage of the N–O bond. A successful debenzylation was achieved in a two-step procedure using 2,2,2-trichloroethyl chloroformate (TrocCl). However, the protection of the hydroxy group was required first (for the reaction of 8b with benzoyl chloride, see Supporting

• was successfully used for the inversion of the C-3/4-trans relative configuration of the isoxazolidine ring. The bulkier ʟ-selectride showed an excellent selectivity toward the C-3/4-cis isomer compared to lithium borohydride. The final N-debenzylation by a two-step procedure involving a basic

Efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates

• Marcin Kaźmierczak and
• Henryk Koroniak

Beilstein J. Org. Chem. 2020, 16, 756–762, doi:10.3762/bjoc.16.69

• into the salts 14 was applied. The salts 14 could be then crystallized and subjected to X-ray studies. A standard N−debenzylation protocol was employed to remove the benzyl protecting group. The hydrogenolysis reaction was catalyzed by palladium on carbon (Pd/C), and was carried out in trifluoroethanol

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• in the pyrrolidine ring catalyzed by RhCl3·H2O, followed by debenzylation, amidation, and aminal generation using the Stille protocol [77]. (–)‐Clavukerin A and related sesquiterpenes Applying original organocatalytic/metal-catalyzed tactics, Metz et al. [78] reported a tandem dienyne RCM for the

Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

• David C. B. Siebert,
• Roman Sommer,
• Domen Pogorevc,
• Michael Hoffmann,
• Silke C. Wenzel,
• Rolf Müller and
• Alexander Titz

Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

• -ᴅ-Ala (16) was coupled to O-benzylserine ethyl ester 37 to give dipeptide 38, hydrogenolytic debenzylation gave the substrate 39 for the copper(I)-mediated elimination of the carbodiimide formed in situ using EDC, and then yielded the dipeptide Boc-ᴅ-Ala-Dha ester 40 in good yields. Lithium

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• selective desilylation and N-debenzylation with simultaneous N-Boc protection and served as a key intermediate for installation of a dimethylhexylene fragment in Julia–Kocienski olefination [56]. Pyrrolidine alkaloids (−)-hygrine ((S)-61) and (−)-hygroline ((2S,2'S)-62) were isolated from many natural

• morpholine first required the reaction with iodotrimethylsilane and furnished diamino alcohol 82 which after N-debenzylation and acylation gave (1R,2R)-81. In a similar way other GCS inhibitors, e.g., ᴅ-threo-P4 (1R,2R)-83a and ᴅ-threo-4'-hydroxy-P4 (1R,2R)-83b (Scheme 20) were obtained and examined as

• group was acquired as shown earlier to provide (2S,3R)-92a and (2S,3R)-92b as N-Boc derivatives after N-debenzylation. Analogues (2S,3R)-89a (DS-SG-44) and (2S,3R)-89b (DS-SG-45) were formed after a regioselective phosphorylation and final treatment with bromotrimethylsilane. DS-SG-44 emerged as an

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• substituents other than fluorine could be prepared, as they were dehalogenated during the final debenzylation. Galectin binding Galectin-1, -3, -4C (C-terminal CRD), -4N (N-terminal CRD), -7, -8C, -8N, -9C, and -9N affinities for (aryltriazolyl)methyl galactopyranosyls 1a–n were determined in a competitive

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• the amine using LiAlH4 with concomitant debenzoylation, followed by the acylation of the amine with lauric acid to afford 9a, and finally, ii) reductive cleavage by hydrogenolysis using Pd–C/H2 leading to debenzylation (Scheme 3). However, during hydrogenolysis, the elimination of the -OBn group led

• to product 9b, which was undesirable. A similar elimination was earlier observed by Sharf et al. during hydrogenolysis of dibenzyl ether [55]. To avoid this, an oxidative debenzylation of 9a using DDQ/CH2Cl2–H2O was carried out. However, this led to a very poor yield of the target compound 2 (Scheme

•  3). Hence, we decided to debenzylate compound 9 prior to its reduction to the amine and subsequent acylation. Towards this (Scheme 4), oxidative debenzylation of 9 using DDQ yielded 10 in 84% yield. Treatment of 10 with LiAlH4 led to the reduction of the azide group to amine along with

Microwave-assisted synthesis of N,N-bis(phosphinoylmethyl)amines and N,N,N-tris(phosphinoylmethyl)amines bearing different substituents on the phosphorus atoms

• Erika Bálint,
• Anna Tripolszky,
• László Hegedűs and
• György Keglevich

Beilstein J. Org. Chem. 2019, 15, 469–473, doi:10.3762/bjoc.15.40

• -tolyl)- or dibenzylphosphine oxide was carried out in acetonitrile at 100 °C for 1 h affording the products with excellent yields (Scheme 4). Then, (aminomethyl)diphenylphosphine oxide (9) was prepared through debenzylation of (benzylaminomethyl)diphenylphosphine oxide (8, Scheme 5). The reduction was

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• -one (4S,5S)-20 after reduction of the carbon–iodine bond formed in the primary products of cyclization (via iodonium ion 22). Hydrogenolytic debenzylation preceded oxidation of the hydroxymethyl group to afford diester (4R,5S)-21 which after hydrolysis gave (2R,3S)-2 as the hydrochloride (Scheme 5