Inositols and Other Cyclohexane Derivatives

The absolute configuration of (—)- and (+)-l,2 4,5-di-0-isopropylidene- wyo-inositol have been assigned as Id and 1l, respectively, by transformation of each enantiomer into an established reference compound. These assigmnents contradict some recent literature reports. (See also Vol. 28, p. 237, ref. 116). 

Heating 1,4,5,6-tetra-O-benzyl-myo-inositol with ethylene carbonate and a trace of sodium bicarbonate affords the 2,3-cyclic carbonate derivative. The reaction fails where there is a trans-diol arrangement as with 1,2,3,6-tetra-O-benzyl-myo-inositol.  

The synthesis of (+)-ononitol (65) and its (—)-enantiomer from resolved myoinositol has been reported. There appears to be a marked abundance of 0-methyl inositols present in grains and forage legumes. 5cy//o-inositol has been per-0-methylated under standard conditions and conformationally examined by NMR spectroscopy.  

Racemic 4-deoxy-4-fluoro-myo-inositol has been made by reaction of 66 with DAST (retention of configuration observed) then hydrogenolysis, and 2-deoxy-2-fluoro-myo-inositol, 2-deoxy-2-fluoro-scy//o-inositol and 2-deoxy-2,2-difluoro-myo-inositol have been synthesized from 3,4,5,6-tetra-O-benzyl-myo-inositol via a selective benzoylation at the equatorial hydroxyl group and subsequent standard chemistry.  

Various cyclitols (and acyclic polyols) have been desynunetrized by formation of dispoke intermediates. (See for example, Vol. 28, p. 237, ref. 115). L-Chiro-inositol can be converted to the silyl derivative 67 in which the trans-diol units are protected on reaction with l,3-dichloro-l,l,3,3-tetraisopropylidisiloxane (TipsQ). Compound 67 was further converted into conduritol B epoxide and its thioepoxide analogue. The conversion of some tetra-O-substituted myo-inosi-tols into adipic dialdehyde derivatives is mentioned in Chapter IS. 

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Inositols and Other Cyclohexane Derivatives - The isoxazolidinocarbocyclic derivative 89 has been produced together with a five-membered carbocyclic compound (diagram 72 in Section 2.1) by cycloaddition from nitrone 73. The formation of 89 predominated in polar protic solvents whilst the reverse was observed in non polar and polar aprotic solvents. 

Inositols and other Cyclohexane Derivatives.-A series of eleven new carba-sugars, termed Gabosines A-K, have been isolated from several Streptomyces strains and are typified by compounds... 

A major fate of PA is conversion to DG that can be metabolized to PC, PE, and TG (Fig. 1). Alternatively, PA can react with CTP to form CDP-DG that is utilized for biosynthesis of the inositol phospholipids as well as phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG) (Fig. 1). Inositol is a cyclohexane derivative in which all six carbons contain hydroxyl groups. The most common inositol isoform is myo-inositol but other less abundant inositols with different structures also occur. The first report of an inositol-containing lipid was in 1930 in Mycobacteria which is ironic since inositol lipids are rarely found in bacteria. Brain is the richest source of inositol-containing lipids, as first discovered by Folch and Wooley in 1942. In 1949, Folch described a PI phosphate (PI-P) that was later found to include PI and PI bisphosphate (PI-P2). The chemical structures of PI, PI-P, and PI-P2 were determined by Ballou and co-workers between 1959 and 1961. PI (1.7 pmol/g liver) constitutes -10% of the phospholipids in cells and tissues. PI-P and PI-P2 are present at much lower concentrations (1-3% of PI). In 1958, Agranoff and co-workers first reported the incorporation of [ HJinositol into PI. Subsequently, Paulus and Kennedy showed that CTP was the preferred nucleotide donor. 

The other phospholipids can be derived from phosphatidates (residue = phosphatidyl). Their phosphate residues are esterified with the hydroxyl group of an amino alcohol choline, ethanolamine, or serine) or with the cyclohexane derivative myo-inositol. Phosphatidylcholine is shown here as an example of this type of compound. When two phosphatidyl residues are linked with one glycerol, the result is cardiolipin (not shown), a phospholipid that is characteristic of the inner mitochondrial membrane. Lysophospholipids arise from phospholipids by enzymatic cleavage of an acyl residue. The hemolytic effect of bee and snake venoms is due in part to this reaction. 

The attempt to obtain structural analogues to phosphatidyl inositols failed. Trihydroxy-cyclohexanes proved not to be substrates of such enzymes, like myoinositol itself and derivatives [151]. The PLD isolated from spinach leaves was reported to be able to give PI as a transphosphatidylation product from PC and inositol [94]. To our knowledge no further exploitation of this method has followed the original article. Other authors have reported the formation of... 

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