Silver complexes bearing trispyrazolylborate ligands (Tp(x)) catalyze the aziridination of 2,4-diene-1-ols in a chemo-, regio-, and stereoselective manner to give vinylaziridines high yields by means metal-mediated transfer NTs (Ts = p-toluensulfonyl) units from PhI═NTs. The preferential occurs at double bond neighboring hydroxyl end ca. 9:1 ratios that assessed very degree regioselectivity. reaction with silver-based catalysts proceeds stereospecific manner, i.e., initial configuration C═C...

Nitrene transfer: Unsymmetric dienes bearing a terminal hydroxy group can be regio- and stereospecifically converted into vinylaziridines upon nitrene transfer from PhINTs using silver-based catalyst. Stoichiometric mixtures of were employed at low catalyst loadings (0.5 %; see scheme). The method has been applied to the synthesis (±)-sphingosine gave good yields in three-step procedure. Ts=4-toluenesulfonyl. Detailed facts importance specialist readers are published as "Supporting...

The first total synthesis of the antivirally active glycolipid cycloviracin B1 (1) is described. approach based on a two-directional strategy which constructs C2-symmetrical macrodiolide core target by an efficient template-directed macrodilactonization reaction promoted 2-chloro-1,3-dimethylimidazolinium chloride 14 as activating agent. Attachment lateral fatty acid chains to lactide thus formed features not only one most advanced ligand-controlled addition reactions functionalized dialkyl...

A general strategy for the synthesis of 2-aryl-glycals and their elaboration to 2-C-aryl-α-glycosides 1,5-anhydro-2-C-aryl-2-deoxy alditols are described. The use reliable, efficient phosphine-free Suzuki–Miyaura cross-coupling 2-iodoglycals in aqueous media as a key step proceeds with complete regioselectivity at C-2 enables access different configurations excellent yields.

A general and efficient protocol for the enantioselective synthesis of sphingosine, phythosphingosine, 4-substituted derivatives was established. These compounds were obtained from a common intermediate prepared butadiene monoepoxide by synthetic sequence involving allylic substitution, cross-metathesis, dihydroxylation.

D- and L-carbocyclic nucleosides were obtained by a new procedure involving an enantioselective rhodium/duphos-catalyzed hydroacylation reaction as the key step. The 3-hydroxymethyl-cyclopentanol intermediate was stereoselective reduction of ketone dynamic kinetic resolution (DKR).

Due to the relevant biological role of sphingosines, ceramides and glycosyl ceramides, increasing demand these compounds for evaluations, developing methods targeting sphingosine phytosphingosine derivatives have attracted interest researchers. The review initially presents structural features compounds, presenting different types nomenclature phytosphingosines, more properties, as well biochemical synthesis. synthetic procedures using products chiral pool, mainly carbohydrates serine...

The dual role of a Rh(<sc>ii</sc>) catalyst both as nitrene transfer agent and Lewis acid in the aziridine ring opening allows regio- stereoselective oxyamination dienyl carbamates.

Abstract Jaspine B and its C‐2 and/or C3 epimers have been enantioselectively prepared from butadiene monoepoxide through a synthetic procedure consisting of allylic amination by palladium‐catalyzed dynamic kinetic asymmetric transformation, cross metathesis, stereoselective dihydroxylation as key steps.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTgem-Difluorination versus 1,2-migration and fragmentation in the reaction of 2- 3-uloses with DAST. Influence stereochemistry at anomeric carbon atomAnas El-Laghdagh, Raouf Echarri, M. Isabel Matheu, Barrena, Sergio Castillon, Jordi GarciaCite this: J. Org. Chem. 1991, 56, 14, 4556–4559Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July...

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTStereoselective Synthesis of 2‘,3‘-Dideoxynucleosides by Addition Selenium Electrophiles to Glycals. A Formal D4T from 2-DeoxyriboseYolanda Díaz, Anas El-Laghdach, Ma Isabel Matheu, and Sergio CastillónView Author Information Departament de Química, Universitat Rovira i Virgili, Pça. Imperial Tarraco 1, 43005 Tarragona, Spain Cite this: J. Org. Chem. 1997, 62, 5, 1501–1505Publication Date (Web):March 7, 1997Publication History Received30 August...

An asymmetric sulfur ylide reaction was employed to prepare an epoxide intermediate in a convergent manner. This efficiently transformed into D-erythro-sphingosine.

Treatment of 2-deoxy-2-iodopyranoses under dehydrative glycosylation conditions afforded pyranose glycals, 2-iodoglycals, and 1,1'-disaccharides instead the expected glycoside products. While product distribution revealed that this reaction is very sensitive to configuration 2-deoxy-2-iodopyranose, 2-iodopyranoid glycals can be obtained almost exclusively in good yields by employing 3,4-O-isopropylidene as a cyclic bifunctional protecting group. The behavior during elimination has been...

Nitrentransfer: Unsymmetrische Diene mit einer endständigen Hydroxygruppe können durch Nitrentransfer von PhINTs in Gegenwart eines Silberkatalysators regio- und stereospezifisch Vinylaziridine umgewandelt werden. Dazu wurden äquimolare Gemische aus Dien sowie nur 0.5 % Katalysator eingesetzt (siehe Schema). Mit dieser Methode war (±)-Sphingosin drei Stufen guten Ausbeuten zugänglich. Ts=4-Toluolsulfonyl. Detailed facts of importance to specialist readers are published as ”Supporting...

Abstract A novel P ‐stereogenic PNP t Bu,Ph ruthenium complex has been synthesized and characterized enabling the asymmetric hydrogenation of a wide range aromatic ketones with excellent catalytic activities (up to 98 % conversion) good levels enantiodiscrimination 95 ee ).

The absolute stereochemistry at the site of attachment fatty acid residues to lactide core glycolipids cycloviracin B1 (1) and glucolipsin A (13) has been elucidated as (3R,3‘R) by comparison their 13C NMR data with those three possible, differently configured structures 9, 12, 14. Moreover, a careful analysis this set allows us conclude that previously proposed for seemingly closely related class antivirally active compounds, i.e., fattiviracin family, need revision. key step en route...

A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosyl glycosides from furanoses is reported. The proposed methodology provides a new route accessing 2-deoxy-oligosaccharides. involves three reactions: Wittig−Horner olefination to give alkenyl sulfanyl derivatives, electrophilic iodine-induced cyclization phenyl 2-deoxy-2-iodo-1-thio-hexo-glycosides, glycosylation. Protected 1, 3, 6−11, which include examples four possible isomeric configurations...

beta-Galactosylceramide and glycolipid analogues were prepared in high yield with complete chemo stereoselectivity by reaction of alpha-iodo glycosides stannyl ceramides, formed situ. TBAI was used to activate both the iodogalactose ether.

The feasibility of using <italic>sc</italic>CO₂ for obtaining glycoconjugates has been demonstrated, by performing metal-free glycosylation without VOCs as solvents.

[reaction: see text] Pyranoid glycals of all configurations can be obtained from pentoses through an olefination-cyclization-elimination sequence. The elimination carried out with excellent yields under radical conditions or by using common reductive reagents such as Zn/Cu, TiCl(4)/LiAlH(4), lithium naphthalenide. proposed method is appropriate for the synthesis allo gulo because cyclization step more efficient these substrates.

Regio- and stereoselective oxyamination of dienes through a tandem rhodium-catalysed aziridination-nucleophilic opening affords racemic oxazolidinone derivatives, which undergo kinetic resolution acylation process with amidine-based catalysts (ABCs) to achieve s values up 117. This protocol was applied the enantioselective synthesis sphingosine.

Abstract A series of 2‐deoxy‐2‐phenylselenenyl‐1‐thioglycosides were evaluated as a class glycosyl donors that provide access to 2‐deoxyglycosides from furanoses. This short synthetic route involves olefination, selenonium ion mediated 6‐endo cyclization and glycosylation reactions. The reaction proceeds with complete regio‐ stereoselectivity, which are enhanced by employing 3,4‐ O ‐isopropylidene cyclic bifunctional protecting group. implication the phenylselenenyl group at C‐2 in...