Dehydrative glycosidations of 2-deoxysugar derivatives catalyzed by an arylboronic ester.

An N-methylpyridinium-4-boronic ester acts as a catalyst for dehydrative glycosidations of 2-deoxy sugar-derived hemiacetals. The catalytic protocol is tolerant of functionalized acceptors, including alcohols bearing isopropylidene ketal, tert-butyl carbamate or benzyl carbamate groups. The results demonstrate that organoboron-catalyzed substitution reactions of alcohols, which have previously been conducted on π-activated (benzylic, allylic or propargylic) substrates, can also be used to achieve C-O bond formation from carbohydrate-derived hemiacetals.

Boronic Acids as Phase-Transfer Reagents for Fischer Glycosidations in Low-Polarity Solvents.

Protocols employing phenylboronic acid as a phase-transfer reagent for Fischer glycosidations in low-polarity organic solvents are described. In addition to providing rate acceleration, the formation of a substrate-derived boronic ester alters the course of the reaction by selective promotion of a furanoside- or pyranoside-selective pathway. Computational modeling of the relative energies of the glycoside-derived boronic esters provides results that are qualitatively consistent with the observed distributions of furanoside versus pyranoside products.

Missense mutation in APOC3 within the C-terminal lipid binding domain of human ApoC-III results in impaired assembly and secretion of triacylglycerol-rich very low density lipoproteins: evidence that ApoC-III plays a major role in the formation of lipid precursors within the microsomal lumen.

Hepatic assembly of triacylglycerol (TAG)-rich very low density lipoproteins (VLDL) is achieved through recruitment of bulk TAG (presumably in the form of lipid droplets within the microsomal lumen) into VLDL precursor containing apolipoprotein (apo) B-100. We determined protein/lipid components of lumenal lipid droplets (LLD) in cells expressing recombinant human apoC-III (C3wt) or a mutant form (K58E, C3KE) initially identified in humans that displayed hypotriglyceridemia. Although expression of C3wt markedly stimulated secretion of TAG and apoB-100 as VLDL(1), the K58E mutation (located at the C-terminal lipid binding domain) abolished the effect in transfected McA-RH7777 cells and in apoc3-null mice.