Alcoholic hydroxyl

In keeping with its biogenetic origin m three molecules of acetic acid mevalonic acid has six carbon atoms The conversion of mevalonate to isopentenyl pyrophosphate involves loss of the extra carbon as carbon dioxide First the alcohol hydroxyl groups of mevalonate are converted to phosphate ester functions—they are enzymatically phosphorylated with introduction of a simple phosphate at the tertiary site and a pyrophosphate at the primary site Decarboxylation m concert with loss of the terti ary phosphate introduces a carbon-carbon double bond and gives isopentenyl pyrophos phate the fundamental building block for formation of isoprenoid natural products... 

See also C. B. Reese, Protection of Alcoholic Hydroxyl Groups and Glycol Systems, in Protective Groups in Organic Chemistry, J. F. W. McOmie, Ed., Plenum, New York and London, 1973, pp. 95-143 H. M. Flowers, Protection of the Hydroxyl Group, in The Chemistry of the Hydroxyl Group, S. Patai, Ed., Wiley-Interscience,... 

The mechanism of anhydride hardening is complex but the first stage of reaction is believed to be the opening of the anhydride ring by an alcoholic hydroxyl group (or salt or a trace of water), e.g. Figure 26.6. 

Codeine, C18H21O3N. This alkaloid was isolated from opium by Robiquet in 1833. It occurs in opium to the extent of 0-1 to 3 per cent., and is isolated therefrom as the hydrochloride along with morphine hydrochloride in the first stage of Gregory s process. It is a methyl ether of morphine and is usually made from the latter by methylation, for which there are numerous patents. An extensive series of ethers of morphine and its isomerides, including ethers of the alcoholic hydroxyl group (Aeterocodeines) has been prepared by Faris and SmaU. ... 

Jsomerides of Morphine and Codeine. When morphine is treated with thionyl chloride, phosphorus trichloride or tribromide, the alcoholic hydroxyl group is replaced by the halogen, forming a-chloromorphide and bromomorphide respectively. The former on treatment with concentrated hydrochloric acid is converted into /3-chloromorphide. Schopf and Hirsch have provided evidence that the two are structural isomerides. With the same reagents codeine yields a parallel set of compounds, viz., a- and -chlorocodides, and bromocodide. The chief characteristics of these products may be summarised thus —... 

Thus, the acidity oi a lactam is evidently not a reliable quantity for predicting the course of the methylation. The acidity gives information only as to the reaction velocity. In this connection the reaction course of isomethylreductone (6) is illuminating, " With diazomethane in ether containing 1 mole of water, the enolraethyl ether (7) is formed. However, if water is present only in traces, then the alcoholic hydroxyl group is selectively attacked to give 8. 

Although the previous example involving a / -hydroxysulfoximine still relies on the involvement of an alcohol, hydroxyl groups are not unique in their ability to... 

This is followed by hydrolysi.s of the ester moieties with potassium carbonate and reesterification of the carboxy moiety with diazomethane to produce intermediate 65. The solitary free alcoholic hydroxyl at C-9 is oxidized with Collins reagent and the silyl ether groups are removed with acetic acid to give enprostil (63) [15]. 

O The alcohol hydroxyl group reacts with POCI3 to form a dichlorophosphate intermediate. 

Table IV presents the results of the determination of polyethylene radioactivity after the decomposition of the active bonds in one-component catalysts by methanol, labeled in different positions. In the case of TiCU (169) and the catalyst Cr -CjHsU/SiCU (8, 140) in the initial state the insertion of tritium of the alcohol hydroxyl group into the polymer corresponds to the expected polarization of the metal-carbon bond determined by the difference in electronegativity of these elements. The decomposition of active bonds in this case seems to follow the scheme (25) (see Section V). But in the case of the chromium oxide catalyst and the catalyst obtained by hydrogen reduction of the supported chromium ir-allyl complexes (ir-allyl ligands being removed from the active center) (140) C14 of the...

Hydrolysis of epoxides Coupling of alcohols Hydroxylation of alkenes... 

Here the alcoholic hydroxyl is first protonated and then eliminated as water. The allylcarbenium ion (2) is initially stabilized by elimination of the proton at C-14. Then the ether link is opened after protonation of the ring oxygen with the formation of carbenium ion (3), whereby the neighboring C-C bond of the piperidine ring is cleaved with aromatization of the C ring. The carbenium ion (4) formed is stabilized by elimination of a proton and ring closure to apomorphine (5). 

This study demonstrates that the addition of the 2-diazopropane with the triple bond of propargyl alcohols is regioselective, and affords new antibacterial 3H-pyrazoles. The photochemical reaction of these 3H-pyrazoles selectively leads to a- and 6-hydroxy cyclopropenes. The overall transformation constitutes a simple straightforward route to substituted cyclopropenyl alcohols without initial protection of the propargyl alcohol hydroxyl group. 

Alcoholic hydroxyl (a) At any given chain length, permeability u-Propanol CH3CH2CH2OH 0.021... 

The alcohol hydroxyl hydrogen typically produced a broad H NMR signal of variable chemical shift which can be eliminated by exchange with deuterium from D20. 

Remarks on 1 and 2.—These two reactions are special cases of a general change, namely, the substitution of an alcoholic hydroxyl group by a halogen atom. This substitution can be carried out in two ways first, as in the preparation of ethyl bromide, 1, by acting on alcohols with hydrogen halides, e.g. 

The hydroxyl of a COOH-group may be replaced by chlorine by means of reactions, in part similar to that described above for the replacement of alcoholic hydroxyl groups by halogen. 

Acylation of the alcohol hydroxyl of the cinchona alkaloid lowers the reaction rate by a factor of 100 while lowering the e.e. to 10%. 

Alcohols are hydroxylated alkyl-compounds (R-OH) which are neutral in reaction due to their unionizable (OH) group (e.g., methanol, ethanol, isopropanol, and w-butanol). The hydroxyl of alcohols can displace water molecules in the primary hydration shell of cations adsorbed onto soil-solid and sediment-solid clay particles. The water molecule displacement depends mainly on the polarizing power of the cation. The other adsorption mechanisms of alcohol hydroxyl groups are through hydrogen bonding and cation-dipole interactions [19,65],... 

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