Sulfonate protecting groups. Regioselective sulfonylation of myo-inositol orthoesters-improved synthesis of precursors of D- and L-myo-inositol 1,3,4,5-tetrakisphosphate, myo-inositol 1,3,4,5,6-pentakisphosphate and related derivatives

Regioselective polymethylation of α-(1 → 4)-linked mannopyranose oligosaccharides

An approach has been developed of the regioselective methylation of α-(1 → 4)-linked mannopyranose oligosaccharides via a four-step methodology. The key reaction involved n-Bu2SnCl2-mediated activation of cis-diols. By tuning protecting groups on the substrates, multiple cis-diols in the substrates were functionalized in a consistent and regioselective manner. Using optimized substrates and reaction conditions, regioselective methylation of di-, tri-, and tetrasaccharide substrates proceeded in isolated yields per cis-diol of 95, 88 and 79%, respectively. The methodology was also applied to functionalize trans-diols in α-cyclodextrin.

Regioselective opening of myo-inositol orthoesters: mechanism and synthetic utility

Acid hydrolysis of myo-inositol 1,3,5-orthoesters, apart from orthoformates, exclusively affords the corresponding 2-O-acyl myo-inositol products via a 1,2-bridged five-membered ring dioxolanylium ion intermediate observed by NMR spectroscopy. These C-2-substituted inositol derivatives provide valuable precursors for rapid and highly efficient routes to 2-O-acyl inositol 1,3,4,5,6-pentakisphosphates and myo-inositol 1,3,4,5,6-pentakisphosphate with biologically interesting and anticancer properties. Deuterium incorporation into the α-methylene group of such alkyl ester products (2-O-C(O)CD2R), when the analogous alkyl orthoester is treated with deuterated acid, is established utilizing the novel orthoester myo-inositol 1,3,5-orthobutyrate as an example. Such deuterated ester products provide intermediates for deuterium-labeled synthetic analogues. Investigation into this selective formation of 2-O-ester products and the deuterium incorporation is presented with proposed mechanisms from NMR experiments.

Synthesis of a new class of β-iodo N-alkenyl 2-pyridones

A new method for the synthesis of β-iodo N-alkenyl 2-pyridones from substituted 2-propargyloxypyridines has been discovered . These compounds present a unique complement of orthogonal functionality and structural characteristics that are unavailable via other routes. The ready access to these compounds renders them an important entry point for the preparation of more complex N-alkyl pyridone-containing targets.

scyllo-inositol pentakisphosphate as an analogue of myo-inositol 1,3,4,5,6-pentakisphosphate: chemical synthesis, physicochemistry and biological applications

myo-Inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P(5)), an inositol polyphosphate of emerging significance in cellular signalling, and its C-2 epimer scyllo-inositol pentakisphosphate (scyllo-InsP(5)) were synthesised from the same myo-inositol-based precursor. Potentiometric and NMR titrations show that both pentakisphosphates undergo a conformational ring-flip at higher pH, beginning at pH 8 for scyllo-InsP(5) and pH 9 for Ins(1,3,4,5,6)P(5). Over the physiological pH range, however, the conformation of the inositol rings and the microprotonation patterns of the phosphate groups in Ins(1,3,4,5,6)P(5) and scyllo-InsP(5) are similar. Thus, scyllo-InsP(5) should be a useful tool for identifying biologically relevant actions of Ins(1,3,4,5,6)P(5), mediated by specific binding sites, and distinguishing them from nonspecific electrostatic effects. We also demonstrate that, although scyllo-InsP(5) and Ins(1,3,4,5,6)P(5) are both hydrolysed by multiple inositol polyphosphate phosphatase (MINPP), scyllo-InsP(5) is not dephosphorylated by PTEN or phosphorylated by Ins(1,3,4,5,6)P(5) 2-kinases. This finding both reinforces the value of scyllo-InsP(5) as a biological control and shows that the axial 2-OH group of Ins(1,3,4,5,6)P(5) plays a part in substrate recognition by PTEN and the Ins(1,3,4,5,6)P(5) 2-kinases.

Glycosynthase-Assisted Synthesis of Some Glycosylated scyllo-Inositols

Three derivatives of scyllo-inositol, a 4-nitrophenyl ether, a benzyl ether, and an ester of 4-toluenesulfonic acid, have been treated with α-d-galactopyranosyl fluoride and a glycosynthase to give the corresponding mono-glycosylated inositols. In one instance, a similar treatment with α-d-glucopyranosyl fluoride gave a mono- and a di-glycosylated inositol.

Sulfonate protecting groups. Improved synthesis of scyllo-inositol and its orthoformate from myo-inositol

A convenient high yielding method for the preparation of scyllo-inositol and its orthoformate from myo-inositol, without involving chromatography is described. myo-Inositol 1,3,5-orthoformate was benzoylated to obtain 2-O-benzoyl-myo-inositol 1,3,5-orthoformate. This diol was tosylated and the benzoyl group removed by aminolysis in a one-pot procedure to obtain 4,6-di-O-tosyl-myo-inositol 1,3,5-orthoformate. Swern oxidation of the ditosylate, followed by sodium borohydride reduction and methanolysis of tosylates gave scyllo-inositol 1,3,5-orthoformate (isolated as the triacetate). Aminolysis of the acetates followed by acid hydrolysis of the orthoformate moiety with trifluoroacetic acid gave scyllo-inositol in an overall yield of 64%.