Inositols acetylation

The vibo or dl (124/35) quercitol (4) needed for the synthesis was prepared from rat/o-inositol (2) via the bromoquercitol (3) according to the method of McCasland and Horswill, (28). By acetonation, acetylation, deacetonation, and equatorial mesylation the mesyloxy derivative... 

One of the most interesting stereospecific dependences which followed from the original study (38,39) of O-acetylated hexopyranose and pento-pyranose derivatives was that of the anomeric proton shifts. In general it was found that the axially oriented anomeric protons gave resonances to higher field than the equatorially oriented protons. Many subsequent studies of pyranose derivatives (24,40) and of inositol derivatives (43)... 

Covalent regulation. Following occupation and activation of the M2 acetyl choline receptors, phospholipase C (PLC), is activated and both inositol (l,4,5)-trisphosphate (IP3), and diacylglycerol (DAG), are formed by hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP2). 

Conduritols and inositols are cyclic polyalcohols with significant biological activity. The presence of four stereogenic centers in the stmcture of conduritols allows the existence of 10 stereoisomers. Enzymatic methods have been reported for the resolution of racemic mixtures or the desymmetrization of meso-conduritols. For example, Mucor miehei lipase (MML) showed enantiomeric discrimination between all-(R) and all-(S) stereoisomers ofconduritol E tetraacetate (Figure 6.52). Alcoholysis resulted in the removal of the four acetyl groups ofthe all-(R) enantiomer whereas the all-(S) enantiomer was recovered [141]. 

C17H24012 ( )-2-(Acetoxy methyl)-1,3,4,6-tetra-O-acetyl-epi-inositol AXMAIN 31 354... 

As these acetals could be converted into the 4,6-O-ethylidene derivatives on treatment with acid, it was reasoned that use of a cyclic vinyl ether, namely, 3,4-dihydro-2H-pyran, might prevent this second process, thus leading to a more useful method of selective acetalation.338 An equimolar reaction with methyl a-D-glu-copyranoside for 4 days in N,N-dimethylformamide led to utilization of 88% of the glycoside, and the 6-(tetrahydropyran-2-yl) ether constituted —85% of the crude reaction-product. In contrast to the steric control apparent in this instance, reaction of 3,4-dihydro-2H-pyran with the axial and equatorial hydroxyl groups in dl-1,4,5,6-tetra-O-acetyl-mi/o-inositol was completely unselective,339 a fact that has been rationalized310 in terms of the probable mechanism of these reactions. 

Selective replacement of hydroxyl groups by bromine has been reported for some inositols and inosamines. DL-2-Amino-2-deoxy-epi-inositol hydrochloride plus acetyl bromide in acetic anhydride gave, after 6 hours at 150°, DL-4-acetamido-l,2,6-tri-0-acetyl-3,5-dibromo-3,4,5-trideoxy-c/uro-inositol in 32% yield, the bromine atoms having been introduced with inversion.407 Under related conditions, DL-epi-... 

In a study of isomerization in some partially acetylated derivatives of mt/o-inositol, weak bases were found to catalyze migration between all of the oxygen atoms, and cis and trans migrations occurred with almost equal facility.546 Equilibration of DL-2-O-acetyl-... 

Tetra- and DL-l,3,4,5,6-penta-0-acetyl-myo-inositol gave, at 120°, the 1,3-di-O-p-tolylsulfonyl and 3-O-p-tolylsulfonyl derivatives, respectively. At room temperature, esterification was not accompanied by migration. 

Epididymis Carnitine Inositol Phosphatidylcholine Cholesterol Glycoproteins Facihtates acetyl-CoA oxidation by spermatozoa (Chapter 9) Precursor for formation of phosphatidyhnositol bisphosphate Buffer to maintain pH and a source of chohne Stabilises membranes They coat the surface of the sperm to protect against IgA... 

AF-DX 116, ll-( 2-[(diethylamino)methyl]-l-piperidinyl acetyl)-5,ll-dihydro-6H-pyrido-[2,3-b](l,4)benzodiazepine-6-one DAG, diacylglycerol IP3, inositol trisphosphate 4-DAMP, 4-diphenylacetoxy-/V-methylpiperidine. 

Occasionally, a per-O-acetylated amine can be used in the synthesis of a partially acetylated compound. For example, 2-amino-2-deoxy-neo-inositol pentaacetate, which was prepared from hygromycin A, was converted by deamination into 1,2,3,4,6-penta-O-acetyl-myo-inositol.226... 

Acetylation of oryo-Inositol. A mixture of mt/o-inositol (5 grams), acetic anhydride (40 ml), methyl sulfoxide (50 ml), and K-t-BuO (2 grams) was stirred at 70°C (water bath, hood) for 45 min and kept overnight at room temperature. Decomposition of the brown reaction mixture with water gave mt/o-inositol hexaacetate (mp 212°-214°C) in 85% yield. Thin layer chromatography (TLC) and NMR analysis of the crude product showed only a trace proportion of an aromatic component. 

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