Anhydride bond, cleavage

Hydrolases catalyze the hydrolytic cleavage of C—C, C—O, C—N, P—O, and certain other bonds, including acid anhydride bonds. 

Tetrahydroprotoberberines (59) having a phenolic hydroxyl group were heated in trifluoroacetic anhydride in a sealed tube to afford the indene derivatives (60) after treatment with methanol (Scheme 14) (57). The products formed through both C-14—N and C-8—N bond cleavage followed by ring closure. 

Hydrolases catalyze the hydrolytic cleavage of C-0, C-N, C-C, and some other bonds including phosphoric anhydride bonds. They possess several attractive features, such as broad substrate selectivity and high stereospecificity. This has made them a popular choice for the conduction of many biotransformafions as well as a powerful addition to the organic chemistry toolbox. Hydrolases also often catalyze several related reactions, such as condensations and alcoholysis. 

Hydrolysis of ATP to ADP is rationalized as nucleophilic attack of water on to the terminal P=0 double bond, followed by cleavage of the anhydride bond and expulsion of ADP as the leaving group. 

In standard conditions, the change in free enthalpy AG° (see p. 18) that occurs in the hydrolysis of phosphoric acid anhydride bonds amounts to -30 to -35 kj mol at pH 7. The particular anhydride bond of ATP that is cleaved only has a minor influence on AG° (1-2). Even the hydrolysis of diphosphate (also known as pyrophosphate 4) still yields more than -30 kJ mol . By contrast, cleavage of the ester bond between ribose and phosphate only provides -9 kJ mol (3). 

The subsequent cleavage of the thio-ester succinylCoA into succinate and coenzyme A by succinic acid-CoA ligase (succinyl CoA synthetase, succinic thiokinase) is strongly exergonic and is used to synthesize a phosphoric acid anhydride bond ( substrate level phosphorylation , see p. 124). However, it is not ATP that is produced here as is otherwise usually the case, but instead guanosine triphosphate (CTP). However, GTP can be converted into ATP by a nucleoside diphosphate kinase (not shown). 

Bond cleavage occurs here in an acid anhydride. 

There are several methods reported in the literature for transforming vicinal diols into ct-diketones while avoiding the risk of C-C bond cleavage.26 Examples include the standard Swem conditions (dimethyl sulfoxide and oxalyl chloride followed by triethylamine), or the use of DMSO activated by acetic anhydride, pyridine-sulfur trioxide complex, or dicyclohexylcarbodiimide (Mq/J-att oxidation). Diones are also obtained by treatment with benzalacetone as a hydride acceptor in the presence of catalytic amounts of tris(triphenylphosphine)ruthenium dichlonde [(PPh RuCFl.27 Recent developments include the use of w-iodoxyben/.oic acid28 or the oxoammonium salt of 4-acctamidoletramethylpipcridine-1-oxyl and y -toluencNulfonic acid.29... 

Radical-based dephosphorylation via a phosphonyl radical constitutes one formulation for the mechanism of C-P bond cleavage during microbial degradation of organophospho-nates.80 Frost has demonstrated that anhydrides 117 derived from phosphonic acid and thiohydroxamic acid react in a chain sequence with thiols, Bu3SnH and CC14 to give dephosphoryl-... 

The itnido complexes [M(NBu-t)2(CH=PPh3)Cl] (M = Mo, W) react with 245 to afford complexes 246 resulting after a C—O bond cleavage and the migration of the ylide ligand to the carbonyl carbon atom. [Os3H2(CO)io] reacts with maleic anhydride... 

Free radical-induced additions have been used in the synthesis of a range of phosphines bearing other nucleophilic groups, e.g., (41), useful for specific peptide bond cleavage of proteins.A further example of the formation of the phosphorinanone system by addition of phenylphosphine to a divinyl ketone derivative has been described.Two reports have appeared of the addition of secondary phosphines to maleic anhydride and related activated olefins, to give functionalised tertiary phosphines, e.g., (42). A route to allylphosphines is provided by base-... 

Other substituted-benzyl glycosides that can be selectively removed in the presence of unsubstituted benzyl ethers have been developed. For example, 2-(hydroxycarbonyl)benzyl glycosides are easily sovolyzed by treatment with Tf20 in the presence of di-tert-butylmethyl-pyridine (DBMP). The reaction implies anomeric C-0 bond cleavage since it takes place by lactonization via the mixed anhydride to generate phthalide and the oxocarbenium ion ( Scheme 71) [399]. 

Keywords C-0 bond cleavage, Activation of C-0 bonds, Oxidative addition, Transition metal complexes, Allylic compounds, Esters, Ethers, Anhydrides, Alcohols... 

---