Laura Poletti

Synthesis of disaccharidic sub-units of a new series of heparin related oligosaccharides

The chemical synthesis of disaccharides1 and2, useful building-blocks for the preparation of a new series of heparin related oligosaccharides containing the unusual sequence (GlcN-IdoA)n, is described. In addition, the orthogonality of the protective groups would allow access to a wide array of differently sulfated oligosaccharides. As the simplest members of this new class of oligomer, the synthesis of sulfated disaccharides3 and4 fully deprotected is reported. Compounds1 and2 have been synthesised as building blocks for a new family of heparin related oligosaccharides containing the unusual sequence (GlcN-IdoA)n. In addition, the orthogonality of the protective groups would allow access to a wide array of differently sulfated oligosaccharides. Download full-size image

Dentoalveolar class III treatment using retromolar miniscrew anchorage

In this article, we report the successful use of miniscrews in the distalization of the lower dentition to correct an Angle class III malocclusion with lower anterior crowding in a dolichofacial adult patient. Conventional intraoral and extraoral appliances have many disadvantages, including the need for patient cooperation, potential for anchorage loss, and vertical extrusion of upper molars and lower incisors. Extrusion should be prevented or minimized when treating long-faced patients with reduced overbite. After third molar extractions, miniscrews were placed in the retromolar area. A sliding jig was applied to distalize the lower molars, while the anterior teeth were bonded and retracted secondarily to avoid round tripping. After 18 months of treatment, molar and canine class I relationship with normal overjet and overbite were achieved. In addition, there was an esthetic improvement in the profile with only a small increase of the lower anterior facial height. These results remained stable at a 12-month follow-up.

Hyper-IgE syndrome: dental implications

Hyper-IgE syndrome (HIES) is a rare multisystem disorder with both immunologic and nonimmunological features. It is characterized by extremely elevated IgE serum levels, eczema, and recurrent skin and pulmonary infections. Dental anomalies are often included, such as retention of deciduous teeth together with ectopic eruption or noneruption of permanent teeth. Severe susceptibility to caries and mycotic infections, insufficient transversal diameter of the palate, mucosal plaques, and fissures typically located on the tongue and on the palate are often present. The aim of this study was to review the literature and to report a 6-year observation of 6 patients with HIES (aged 8-39 years) with focus on their oral problems and the treatment provided. The importance of the role of the dentist both in early diagnosis of this syndrome and in monitoring oral conditions was stressed. The dentist can prevent infective complications and intercept the development of malocclusion with a reduction of the need for complex treatment.

Modeling of synthetic phosphono and carba analogues of N-acetyl-α-D-mannosamine 1-phosphate, the repeating unit of the capsular polysaccharide from Neisseria meningitidis serovar A

The conformational behavior of methyl (2-acetamido-2-deoxy-alpha-d-mannopyranosyl)phosphate 1, and its analogues, methyl C-(2-acetamido-2-deoxy-alpha-d-mannopyranosyl)methanephosphonate 2 and methyl O-(2-acetamido-2-deoxy-5a-carba-alpha-d-mannopyranosyl)phosphate , where a methylene group replaces, respectively, the anomeric and the pyranose oxygen atom, was investigated at the B3LYP/6-311+G(d,p) level [6-311+G(2df,p) for the phosphorus atom]. The energy of the optimized structures was recalculated using the continuum solvent model C-PCM choosing water as the solvent. The compounds exhibited several populated conformations, but they all showed a marked preference for the (4)C(1) geometry of the pyranose ring; this preference was almost complete for 1, very large for the phosphono analogue 2, and large for the carba analogue 3. To give experimental support to these results, compounds 2 and 3 were synthesized and characterized by NMR spectroscopy. The comparison of the theoretical and experimental vicinal coupling constants confirmed the marked preference for the (4)C(1) geometry in the case of 2 and suggested that the same holds true for compound 3.

Simple Synthesis of Versatile Coumarin Scaffolds

Abstract We describe an approach using ring‐closing metathesis (RCM) to synthesize versatile coumarin derivatives that present appropriate substitutions both at the aromatic and at the α,β‐unsaturated lactone ring. The obtained compounds can be used as molecular scaffolds suitable for further diversifications through a combinatorial approach.

HRMAS NMR analysis in neat ionic liquids: a powerful tool to investigate complex organic molecules and monitor chemical reactions

The high resolution magic angle spinning (HRMAS) NMR technique proved to be an effective tool for the analysis of organic solutes and for the observation of an organic reaction in neat ionic liquids.

A CONVENIENT MULTIGRAM PREPARATION OF FUNCTIONALIZED 2-AZIDO-2-DEOXY-D-MANNOSE AS A USEFUL ORTHOGONALLY PROTECTED BUILDING BLOCK FOR OLIGOSACCHARIDE SYNTHESIS

Multigram preparation of strategically protected 2-azido-2-deoxy mannose 5 from pentaacetyl glucose 1 is described. This manno-derivative was obtained in a straightforward manner and in high overall yield and represents a flexible building-block for complex oligosaccharide synthesis.

Boranophosphate Diesters as Stable Synthetic Analogues of 1-O-Glycosylphosphates

Different 1-O-glycosylboranophosphate diesters were synthesised as stable analogues of 1-O-glycosylphosphates, using a one-pot procedure based on the anomeric H-phosphonate of 2,3,4-tri-O-benzyl-α-l-rhamnopyranose as a common precursor.

IMPROVEMENT ON LIPASE CATALYSED REGIOSELECTIVE O-ACYLATION OF LACTOSE:A CONVENIENT RUOTE TO 2′-O- FUCOSYLLACTOSE[1]

Although enormous progress has been made in the past ten years, the synthesis of complex carbohydrates still remains a severe problem. Conventional syntheses of these molecules often dictate multiple protections and deprotections of various hydroxyl groups, dramatically increasing the number of steps required. On the other hand, enzymes offer the opportunity to carry out cheap, highly chemo and regioselective transformations, providing new approaches to tackle many synthetic problems encountered in carbohydrate synthesis. In particular, lipases allow highly regioselective O-acylations. Therefore, a growing interest in enzymatic manipulation of protecting groups for the synthesis of oligosaccharides has been developed during recent years. Recently, we reported on the use of lipase catalysed acylation for designing useful building blocks in oligosaccharide synthesis. Excellent selectivity for 6 O-acylation was observed on various disaccharidic substrates (such as lactose, maltose and cellobiose) using different acylating agents, Candida antarctica lipase being the best biocatalyst. However, our procedure contained a main drawback: the high polarity of the sugar substrates required the use of tert-amyl alcohol as a solvent, whose high boiling point made the work up of the reaction mixture quite laborious, thus rendering the method impractical. An important improvement J. CARBOHYDRATE CHEMISTRY, 20(7&8), 761–765 (2001)

Improvement of the Synthesis of Immunological Carbohydrate Vaccines Containing the Tumour Associate Antigen CaMBr1

The simplified synthesis of a portion of Globo-H hexasaccharide, a saccharide antigen overexpressed by breast cancer cells, and its conjugation to two different immunogenic proteins are described. The conjugated vaccines, evaluated in a preclinical model, showed good immunogenic potential.