Stereoselective synthesis of myo-inositol via ring-closing metathesis: a building block for glycosylphosphatidylinositol (GPI) anchor synthesis

Stereoselective α-glycosylation of C(6)-hydroxyl myo-inositols via nickel catalysis-application to the synthesis of GPI anchor pseudo-oligosaccharides

Glycosylphosphatidyl inositol (GPI) anchors play a key role in many eukaryotic biological pathways. Stereoselective synthesis of GPI anchor analogues have proven to be critical for probing the biosynthesis, structure, and biological properties of these compounds. Challenges that have emerged from these efforts include the preparation of the selectively protected myo-inositol building blocks and the stereoselective construction of glucosamine α-linked myo-inositol containing pseudodisaccharide units. Herein, we describe the effectiveness of the cationic nickel(II) catalyst, Ni(4-F-PhCN)4(OTf)2, at promoting selective formation of 1,2-cis-2-amino glycosidic bonds between the C(2)-N-substituted benzylideneamino trihaloacetimidate donors and C(6)-hydroxyl myo-inositol acceptors. This catalytic coupling process allows rapid access to pseudosaccharides of GPI anchors in good yields and with excellent levels of α-selectivity (α:β=10:1-20:1). In stark contrast, activation of trichloroacetimidate donors containing the C(2)-N-substituted benzylidene group with TMSOTf and BF3(.)OEt2 provided the desired pseudodisaccharides as a 1:1 mixture of α- and β-isomers.

Synthesis of mycobacterial triacylated phosphatidylinositol dimannoside containing an acyl lipid chain at 3-O of inositol

A seven-step synthesis of triacylated phosphatidylinositol dimannoside is described from myo-inositol 1,3,5-orthoformate. It proceeded in 31% overall yield via a highly regioselective and stereoselective 2,6-di-O-D-mannosylation as the key step.

A powerful reagent for synthesis of Weinreb amides directly from carboxylic acids

A powerful reagent, P[NCH(3)(OCH(3))](3) (3), for conversion of carboxylic acids directly to Weinreb amides was developed. In most cases the yields of the corresponding Weinreb amides were above 90% when P[NCH(3)(OCH(3))](3) was heated with aromatic and aliphatic carboxylic acids in toluene. The sterically hindered carboxylic acids can also give the corresponding Weinreb amides in excellent yields.

Application of the Quiral Program to the Challenge of Myoinositol Synthesis

The Quiral program helps chemists to choose synthetic approaches to myoinositol or its protected derivatives.

Synthesis and Characterization of Covalent Mimics of Phosphatidylinositol-4,5-bisphosphate Micelles

There is increasing evidence that multivalency plays an important role in protein-lipid recognition and membrane targeting in biological systems. We describe here the preparation and characterization of multivalent analogues of the signaling lipid phosphatidylinositol-4,5-bisphosphate (PIP2). Tetherable analogues of the PIP2 headgroup were appended to polyamidoamine dendrimers via a squarate linker to afford polymers displaying four or eight headgroup moieties. This class of molecules should provide a powerful tool for the study of protein-lipid interactions.

The structure and mechanism of myo-inositol-1-phosphate synthase

The first and rate-limiting step in the biosynthesis of myo-inositol is the conversion of D-glucose 6-phosphate to 1L-myo-inositol 1-phosphate catalyzed by 1L-myo-inositol 1-phosphate synthase (MIP synthase). MIP synthase has been identified in a wide variety of organisms from bacteria to humans and is relatively well-conserved throughout evolution. It is probably homotetrameric in most if not all cases and always requires NAD+ as a cofactor, with NADH being reconverted to NAD+ in the catalytic cycle. This review focuses on the structure and mechanism of MIP synthase, with a particular emphasis on the mechanistic insights that have come from several recent structures of the enzyme. These include the structure of the enzyme from Saccharomyces cerevisiae, Archeoglobus fulgidus and Mycobacterium tuberculosis.

Studies into the stereoselectivity of tartrate-derived dienophiles

[reaction: see text] Diels-Alder reactions of 1-(tert-butyldimethylsiloxy)-1,3-butadiene (3) with three C2 symmetric dienophiles derived from tartaric acid have been examined. Complementary diastereoselectivity is observed depending on the nature of the 1,2-diol protecting group incorporated in these dienophiles.

A concise synthetic route to the conduritols from pentoses

A short synthetic strategy for preparation of the conduritols is described. The key step employs a zinc-mediated fragmentation of protected methyl 5-deoxy-5-iodo-d-pentofuranosides followed by an allylation of the intermediate aldehyde in the same pot. The allylation is performed with 3-bromopropenyl benzoate and occurs with good diastereoselectivity. An amino group can be introduced in the product by trapping the intermediate aldehyde as the imine prior to the allylation. The functionalised 1,7-octadienes, thus obtained, are converted into protected conduritols by ring-closing olefin metathesis.

Common-intermediate strategy for synthesis of conduritols and inositols via beta-hydroxy cyclohexenylsilanes

[reaction: see text] Syntheses of conduritols B-D and F and d-(+)-chiro- and neo-inositols from cyclohexenylsilane intermediates are described. The key cyclohexylsilane intermediates 5 and 14 were synthesized by stereoselective olefin dihydroxylation of the corresponding cyclohexenylsilanes. Selective Peterson elimination reactions and Fleming-Tamao oxidations of 5 and 14 then delivered the targeted cyclitol derivatives.