A convergent synthetic route to a tetrasaccharide related to PI-88, which allows the incorporation of a fluorescent BODIPY-label at the reducing-end, has been developed. The strategy, which features the use of 1,2-methyl orthoesters (MeOEs) as glycosyl donors, illustrates the usefulness of suitably-designed BODIPY dyes as glycosyl labels in synthetic strategies towards fluorescently-tagged oligosaccharides. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Novel, linker-free, BODIPY-carbohydrate derivatives containing sugar residues at positions C2 and C6 are efficiently obtained by, hitherto unreported, Ferrier-typeC-glycosylation of 8-aryl-1,3,5,7-tetramethyl BODIPYs with commercially available tri-O-acetyl-glucal followed by saponification. This transformation, which involves the electrophilic aromatic substitution (SEAr) of the dipyrrin framework with an allylic oxocarbenium ion, provides easy access to BODIPY-carbohydrate hybrids with excellent photophysical properties and a weaker tendency to aggregate in concentrated water solutions. © 2021 The Authors. Published by American Chemical Society

Hitherto unreported 2,6-dipropargyl-1,3,5,7-tetramethyl BODIPYs can be efficiently prepared by a Nicholas reaction/decomplexation protocol from 1,3,5,7-tetramethyl BODIPYs. The title compounds, which improve the BODIPY photostability by retaining their inherent photophysical and photochemical properties, can be engaged in efficient copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click-typereactions with azido derivatives to provide all-BODIPY-triads or conjugated BODIPYs. © 2021 The Authors. Published by American Chemical Society.

A series of fluorescent boron-dipyrromethene (BODIPY, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes have been designed to participate, as aglycons, in synthetic oligosaccharide protocols. As such, they served a dual purpose: first, by being incorporated at the beginning of the process (at the reducing-end of the growing saccharide moiety), they can function as fluorescent glycosyl tags, facilitating the detection and purification of the desired glycosidic intermediates, and secondly, the presence of these chromophores on the ensuing compounds grants access to fluorescently labeled saccharides. In this context, a sought-after feature of the fluorescent dyes has been their chemical robustness. Accordingly, some BODIPY derivatives described in this work can withstand the reaction conditions commonly employed in the chemical synthesis of saccharides; namely, glycosylation and protecting-group manipulations. Regarding their photophysical properties, the BODIPY-labeled saccharides obtained in this work display remarkable fluorescence efficiency in water, reaching quantum yield values up to 82 \%, as well as notable lasing efficiencies and photostabilities. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The antimicrobial evaluation of twelve natural and hemisynthetic isopimarane diterpenes are reported. The compounds were evaluated against a panel of Gram-positive bacteria, including two methicillin-resistant Staphylococcus aureus (MRSA) strains and one vancomycin-resistant Enterococcus (VRE) strain. Only natural compounds 7,15-isopimaradien-19-ol (1) and 19-acetoxy-7,15-isopimaradien-3β-ol (6) showed promising results. Isopimarane (1) was the most active, showing MIC values between 6.76 µM against S. aureus (ATCC 43866) and 216.62 µM against E. faecalis (FFHB 427483) and E. flavescens (ATCC 49996). Compound (6) showed moderated activity against all tested microorganisms (MIC between value 22.54 and 45.07 µM). These compounds were found to be active against the methicillin-sensitive strains of S. aureus (CIP 106760 and FFHB 29593), showing MIC values of 13.55 (1) and 22.54 (6) µM. Both compounds were also active against vancomycin-resistant E. faecalis (ATCC 51299) (MIC values of 54.14 and 45.07 µM, respectively). In addition, the cytotoxicity of nine compounds 7,15-isopimaradien-3β,19-diol (2); mixture: 15-isopimarene-8β-isobutyryloxy-19-ol and 15-isopimarene-8β-butyryloxy-19-ol (3); 3β-acetoxy-7,15-isopimaradiene-19-ol (5); 19-acetoxy-7,15-isopimaradiene-3β-ol (6); 3β,19-diacetoxy-7,15-isopimaradiene (8); 15-isopimarene-8β,19-diol (9); 19-O-β-d-glucopyranoside-7,15-isopimaradiene (10); lagascatriol-16-O-β-d-glucopyranoside (11) and lagascatriol-16-O-α-d-mannopyranoside (12) was evaluated in the human breast cancer cell line MDA-MB-231. Isopimarane (2) was the only compound showing some cytotoxicity. The IC50 value of compound (2) was 15 µM, suggesting a mild antiproliferative activity against these breast cancer cells. © 2020 by the authors.

The development of efficient and stable red and near-IR emitting materials under hard radiation doses and/or prolonged times is a sought-after task due to their widespread applications in optoelectronics and biophotonics. To this aim, novel symmetric all-BODIPY-triads, -pentads, and -hexads have been designed and synthesized as light-harvesting arrays. These photonic materials are spectrally active in the 655–730 nm region and display high molar absorption across UV–visible region. Furthermore, they provide, to the best of our knowledge, the highest lasing efficiency (up to 68 \%) and the highest photostability (tolerance >1300 GJ mol−1) in the near-IR spectral region ever recorded under drastic pumping conditions. Additionally, the modular synthetic strategy to access the cassettes allows the systematic study of their photonic behavior related to structural factors. Collectively, the outstanding behavior of these multichromophoric photonic materials provides the keystone for engineering multifunctional systems to expedite the next generation of effective red optical materials. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

A concise synthetic route from methylmalonate to a tetravalent aliphatic scaffold has been developed. The ensuing tetra-tethered derivative is equipped with two hydroxyl groups, as well as orthogonal alkene and alkyne functionalities. The usefulness of the scaffold has been demonstrated with the preparation of two representative multivalent derivatives: (i) a tetravalent compound containing two D-mannose units, one fluorescent boron-dipyrromethene (BODIPY) dye and a suitably functionalized amino acid and (ii) by way of dimerization and saponification, a water-soluble tetramannan derivative containing two fluorescent BODIPY units. Additionally, photophysical measurements conducted on these derivatives support the viability of the herein designed single and double BODIPY-labeled carbohydrate-based clusters as fluorescent markers. © 2019 by the authors.

Glycosylation of alcohol derivatives with D-mannose and D-glucose derived methyl 1,2-orthobenzoates can be promoted by commercially available acid-washed 300 molecular sieves (AW-MS), which functions both as promoter and as a drying agent in an operationally simple process. In this manner, glycosides can be obtained in good to excellent yields at room temperature, reflux, or under microwave (MW) heating. The usefulness of the process has been shown with the preparation of some diterpene glycosides. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Carbapyranoses, i.e., pyranose derivatives whose ring oxygen has been replaced by a methylene group, are currently recognized as valuable carbohydrate mimetics. A plethora of methods are available for their preparation, and among them the radical cyclization of suitably functionalized carbohydrate derivatives has already positioned itself as a reliable synthetic method. The present review aims to give an overview of the different synthetic strategies based on radical cyclization that have been employed in their preparation. Recent contributions from our research group are included, which will serve to delineate the scope and limitations of these methods. © 2014 Bentham Science Publishers.

Carbohydrates have been recognized as privileged structures for the regio- and stereo-controlled appendage of pharmacophores to generate new derivatives with potential application in drug discovery processes. Even though most of the carbohydrate templates have been generated from pyranoses, other sugar derivatives have also been employed in the assembly of such structures. In this review, attention has been directed to the use of sugar-furanose platforms, and an account of the recent developments in the generation of furanose-based templates aiming at the generation of molecular diversity, including those from our research group, is presented. © 2014 Bentham Science Publishers.

Pyranosidic allylic (Ferrier) cations that share dicobalt hexacarbonyl propargyl (Nicholas) stabilization at C-1, can be easily generated by treatment of hexacarbonyldicobalt alkynyl glycals with BF3·OEt2, and display a remarkable reactivity leading to a variety of products. The substituent at O-6 in these glycals plays a pivotal role in directing the outcome of the transformations. Accordingly, 6-O-benzyl or 6-O-allyl groups cause a series of transformations resulting in the stereoselective formation of oxepanes through a process that involves an initial hydride transfer step from the allyl or benzyl substituent to the Ferrier-Nicholas cation. On the contrary, 6-OH derivatives undergo an overall ring contraction to branched tetrahydrofuran derivatives. 6-O-Silyl derivatives, in the presence of heteroaryl nucleophiles, were transformed into C-3 branched bis-C-Cglycosides, containing two of such molecules. © 2014 IUPAC & De Gruyter.

n-Pentenyl glycosides (NPGs) and n-pentenyl orthoesters (NPOEs) have been transformed into glycosyl fluorides by a variety of methods. In the case of NPGs, Barluenga's reagent, bis(pyridinium)iodonium(I)tetrafluoroborate (IPy 2BF4), gives good yields of glycosyl fluorides when HF-pyridine complex is used as an additional fluoride source. NPOEs can be activated either by a combination of electrophilic iodonium (Barluenga's reagent) and HBF4 or by the action of HF-pyridine complex. The ensuing glycosyl fluorides form a semiorthogonal pair of glycosyl donors when confronted with NPGs. © 2012 Published by NRC Research Press.

Glycals (1,2-unsaturated, cyclic carbohydrate derivatives) readily undergo (catalyzed) substitution reactions at C-1 accompanied by allylic rearrangement. This reaction, currently named Ferrier rearrangement, or the Ferrier I reaction, has established itself as a useful synthetic tool for carbohydrate transformations. By means of this reaction, glycals can be converted into highly useful 2,3-unsaturated glycosides. This review summarizes recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals. The (catalyzed) substitution of glycals at C-1, accompanied by allylic rearrangement to give unsaturated glycosides, is known as Ferrier rearrangement, or the Ferrier I reaction. Recent developments in this rearrangement have involved evaluation of new homogeneous and heterogeneous catalysts, as well as its application to nucleophiles other than oxygenated ones (e.g., C-, N-, and S-nucleophiles). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mannopyranose-derived methyl 1,2-orthoacetates (R = Me) and 1,2-orthobenzoates (R = Ph) undergo stereoselective formation of 1α,1′β-disaccharides, upon treatment with BF 3•Et 2O in CH 2Cl 2, rather than the expected acid-catalyzed reaction leading to methyl glycosides by way of a rearrangement-glycosylation process of the liberated methanol. © 2011 American Chemical Society.

Mannopyranose-derived methyl 1,2-orthoacetates (R = Me) and -benzoates (R = Ph) can function as glycosyl donors - upon BF 3·Et 2O activation in CH 2Cl 2 - in glycosylation reactions with monosaccharide acceptors to afford disaccharides in good yields. In the process, glycosylation is preferred to acid-catalyzed rearrangement leading to methyl mannopyranosides. Methyl 1,2-orthoesters can be also used in regioselective glycosylation protocols with monosaccharide diols, in which they display good regioselectivity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly functionalized 1-exo-alkylidene-2,3-anhydro-, and 1'-halo-1-exoalkylidene-2,3-anhydro-furanoses, which are accessible from D-mannose in four or five steps, respectively, can be efficiently transformed in furanose based templates with up to four sites of molecular diversity, by way of a series of chemoselective transformations at their double bond, oxirane, or allylic oxirane, functionalities. © The Royal Society of Chemistry 2012.

A branched Man5 oligosaccharide has been synthesized by sequential regioselective glycosylations on a mannose-tetraol with n-pentenyl orthoester glycosyl-donors promoted by NIS/BF3·Et 2O, in CH2Cl2. An extended n-pentenyl chain was incorporated into the tetraol acceptor to facilitate (a) the solubility of the starting tetraol in CH2Cl2, and (b) future manipulations at the reducing end of the Man5 oligosaccharide. © The Royal Society of Chemistry 2012.

Several synthetic strategies directed towards 5a-carbahexopyranoses and based on 6-endo-trig radical cyclization of unsaturated carbohydrate derivatives have been devised. Three elements for regiocontrol to optimize the 6-endo/5-exo ratio have been incorporated, and their efficiencies in directing 6-endo cyclizations have been evaluated. These elements - namely: i) the incorporation of a substituent at C-5 (radical numbering), ii) the use of a vinyl (rather than alkyl) radical, and iii) the inclusion of ring strain in the system - have proved useful when used in combination. The simultaneous presence of two of them also results in 6-endo selectivity. On another topic, the ozonation of the ensuing alkenylstananes to afford diols seems to be based on a tin-oxygen rearrangement, similar to that reported for related vinylsilanes, rather than on remarkable stabilities of tin-containing primary ozonides as we had previously suggested. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly functionalized 1-exo-alkylidene-2,3-anhydro-, and 1′-halo-1-exo-alkylidene-2,3-anhydrofuranoses can be prepared in four or five steps, respectively, from D-mannose. These compounds feature a variety of functionalities, including a double bond, an oxirane, an allylic oxirane and (in the case of the 1′-halo derivative) an alkenyl halide. The reactivity of each functionality in these derivatives has been explored, and the usefulness of these substrates has been demonstrated with the preparation of furanose-based carbohydrate templates with up to four sites of molecular diversity. A highly functionalized 1-exo-alkylidene-2,3-anhydro-furanose, available in four steps from D-mannose, is a useful substrate that can be transformed into a variety of furanose derivatives including compounds with up to four sites for diversity. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Furanose- and pyranose-derived mono- and dihalo-exo-glycals undergo Sonogashira coupling reactions in the presence of Pd catalysts to give carbohydrate-derived enynes in a completely stereoselective manner. On the other hand, a furanose-derived 2, 3-anhydrohalo-exo-glycal, available from D-mannose in five steps, undergoes Pd0-catalyzed Sonogashira coupling, leading to 2-deoxyenynes. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA,.