Cyclopentenediol

Treatment of perfluoro(l-methylcyclopent-l-ene) with aqueous potassium hydroxide gives cyclopentenediol 15 and in 1.2-dimethoxyethane yields the cyclopentane-1,3-dione derivative... 

Oxypalladation of vinyl ether, followed by alkene insertion, is an interesting synthetic route to functionalized cyclic ethers. In prostaglandin synthesis, the oxypalladation of ethyl vinyl ether (40) with the protected cyclopentenediol 39 generates 41 and its intramolecular alkene insertion generates 42. The intermolecular insertion of the alkene 43, and /1-elimination of 44 occurred as one-pot reaction at room temperature, giving the final product 45 in 72% yield [46], The stereochemistry of the product shows that the alkene insertion (carbopalladation of 41) is syn. It should be noted that the elimination of /1-hydrogen from the intermediate 42 is not possible, because there is no /1-hydrogen syn coplanar to the Pd and, instead, the insertion of alkene 43 occurs. 

The homochiral prostaglandin precursor (15,3fi)-330.1 was prepared [Scheme 4.330] by selective hydrolysis of the /weso-diacetate of cw-4-cyclopentene-13-diol 330 2 using pig liver esterase (PLE),617 whereas the enantiomer (1/ ,35)-330 3 was the product of electric eel cholinesterase (EECE) hydrolysis,618 Since enzyme-catalysed reactions are reversible, transesterification can also be used to prepare esters. In the case at hand, ciy-4-cydopentene-l,3-diol (330.4) was enan-tioselectively transesterified using pig pancreatic lipase (PPL) and trichloroethyl acetate.619 The trichloroethyl ester is used in order to influence the position of equilibrium since trichloroethanol is a better leaving group and weaker nucleophile than cyclopentenediol.620... 

The distillate, containing 2-cydopentenone, water and varying amounts of cyclopentenediols, is dissolved in 150 ml. of methylene chloride and dried over anhydrous sodium sulfate. The solvent is carefully removed through a Vigreux column and the residue purified by distillation. After a forerun (b.p. 50-150°), there is collected 44-49 g. (53-60%) of pure 2-cyclopentenone, b.p. 151-154°. Cyclopentenediols may be recovered from the pot residue by distillation at 0.1 mm. The forerun contains appreciable amounts of cyclopentenone and should be added to a succeeding preparation before final distillation. 

Dienes may be hydroxylated at one or at both double bonds, depending on the amount of oxidants used. Cyclopentadiene, on treatment with an excess of hydrogen peroxide and osmium tetroxide as a catalyst in tert-butyl alcohol, gives a mixture of 21% of 3,5-cyclopentenediol and 61% of 1,2,3,4-cyclopentanetetrol [152. ... 

Slany, R. K., Bosl, M., Crain, R, and Kersten, H. (1993). A new function of S-adenosyl-methionine The ribosyl moiety of AdoMet is the precursor of the cyclopentenediol moiety of the tRNA wobble base queuine. Biochemistry 32, 7811-7817. 

Cyclopentenediol isomers have previously been prepared by hydrolysis of acetates produced by reaction of dibromocyclopen-tene with potassium acetate in acetic acid 2 by reaction of cyclo-pentene with selenium dioxide in acetic anhydride or by reaction of cyclopentadiene with phenyl iodosoacetate,4 with lead tetraacetate,6 or with peracetic acid in the absence of base. Preparation of cyclopentenediol without intermediate formation of acetates has been accomplished by reaction of cyclopentadiene with hydrogen peroxide in the presence of osmium tetroxide in tert-butanol,7 and by reaction of cyclopentadiene with peracetic acid in a methylene chloride suspension of anhydrous sodium carbonate, followed by hydrolysis of the resulting epoxycyclopen tene.8... 

Treatment of 1,4-cyclopentenediol with butyl vinyl ether gives the bicyclic y-laclol, 2-oxabicy-clo[3.3.0]oct-6-en-3-ol (15), in 63% yield406. 

The palladium-catalysed desymmetrization of 2,4-cyclopentenediol has also been studied using a similar approach. See Greenfield, S. J. ... 

The peptide-based phosphine ligand 105 was identified from a polymer-supported phosphine library of 75 members [154]. Enantioposition-selective desymmetrization of the meso-cyclopentenediol derivative 100 was promoted by a palladium complex of 105 to afford the cyclic carbamate 101 with 76% ee. This result demonstrated that the combinatorial approach is effective in the lead-generation stage of stereoselective catalyst development [155, 156]. The resin-supported palladium complex of Ac-D-Phg-Pro-D-Val-Pps-D-Leu-NH resin 106, which has also been developed through the combinatorial approach. 

Additional examples of desymmetrization of meso cyclopentenediol tosylcarba-mates. " ... 

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