Hydroxylation regiospecific

He X, Cryle MJ, De Voss JJ, Ortiz de Montellano PR (2005) Calibration of the channel that determines the co-hydroxylation regiospecificity of cytochrome P4504A1. J Biol Chem 280 22697-22705... 

Ester, ether, and cycHc acetal groups are used as blocking groups to allow regiospecific reactions to take place, ie, reaction at specific unblocked hydroxyl groups. 

Hoomaert has studied Diels-Alder reactions of pyridine oquinodimethane analogs generated from functionalized o-bis(chloromethyl)pyridines <96T(52)11889>. The photochemical cycloaddition of 2-alkoxy-3-cyano-4,6-dimethylpyridine with methacrylonitrile gives a bicyclic azetine, 6-alkoxy-3,5-dicyano-2,5,8-trimethyl-7-azabicyclo[4.2.0]octa-2,7-diene, in moderate yield <96CC1349>. Regiospecific hydroxylation of 3-(methylaminomethyl)pyridine to 5-(methylaminomethyl)-2-(17/)-pyridone by Arthrobacter ureafaciens has been reported <96MI173>. 

Deuterated and tritiated tin hydrides have been used to prepare deuterated saccharides93 and tritiated steroids46 from alkyl bromides, (equations 68 and 69). It is important to note that isomerization has occurred at the chiral reaction centre in the saccharide reaction (equation 68). For the steroid, the tin hydride reaction is regiospecific, i.e. it only reacts at the more reactive bromide rather than the less reactive chloride site and does not react with the keto group, the hydroxyl group or the acetal group. 

The rhodium-catalyzed borylation of alkanes is applied to regiospecific functionalization of polyolefines.165,165a The reaction of polypropylenes (atactic, isotactic, and syndiotactic) with B2pin2 in the presence of Cp Rh( 74-C6Me6) catalyst at 200 °G affords the borylated polymers, which are treated with basic hydrogen peroxide in a mixture of THF and H20 to oxidize the boronate esters to the corresponding alcohols (Scheme 20). The hydroxylated polymers contain 0.2-1.5% hydroxymethyl side-chains. 

Van der Bolt FJT, van den Heuvel RHH, Vervoort J, van Berkel WJH (1997) 19F NMR study on the regiospecificity of hydroxylation of tetrafluoro-4-hydroxybenzoate by wild-type and Y385F p-hydroxybenzoate hydroxylase evidence for a consecutive oxygenolytic dehalogenation. Biochemistry 36 14192-14201... 

Aminosugars are the result of replacement of one or more hydroxyl groups in a sugar by amino groups. They are formed in nature by transamination processes (see Section 15.6) on appropriate keto sugars, which are themselves the product of regiospecific... 

In this particular case, remote control by the heteroatom of the substituent is invoked to explain the regioselectivity of the elimination. Complexation of lithium with both oxygens fixes the basic carbon atom close to the -proton . A similar model is proposed to rationalize the reversal to regiospecific a-deprotonation proximate to the hydroxyl group for oxiranes of type 23, the basic site now being close to the a-proton (Scheme 9) ° . 

Liu, C.J. et al., Regiospecific hydroxylation of isoflavones by cytochrome P450 81E enzymes from Medicago truncatula. Plant J., 36, 471, 2003. 

However, this monosnbstitution is also regiospecific only one derivative is usually isolated. In principle, any pair of hydroxyl groups in a sugar molecule can give two... 

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