2-Hydroxycyclopentanecarboxylic acid

It is important that the synthesis should be carried out as quickly as possible, particularly the washing with alkali at 0 °C, since the latter tends to convert the product into 1-hydroxycyclopentanecarboxylic acid. 

The reaction with captodative stabilized radicals is also possible [82]. For instance, the preparation of 1-hydroxycyclopentanecarboxylic acid derivatives from a chiral glycolic acid equivalent is reported [83]. Cyclization and annula-tion procedures are depicted in Eqs. 32 and 33, respectively. 

Base-catalyzed rearrangement of a-haloketones to acids or esters. The rearrangement of a, oc -dibromocyclohexanones to 1-hydroxycyclopentanecarboxylic acids, followed by oxidation to the ketones is known as the Wallach degradation ... 

In an extension of work reported last year, it has been found that cis-2-hydroxycyclopentanecarboxylic acid yields the cis-/3-lactone (29) on treatment with tosyl chloride in pyridine. By contrast, the rran -isomer undergoes simple dehydration under these conditions. 

Methyltetrahydropyran-2-ylacetic acid, A"6.16 2-Cyclohexyl-2-hydroxyacetic acid, A"14.7 2-Hydroxycyclopentanecarboxylic acid ethyl... 

While a t-butyl group has little influence on reactivity in a 1,3-disubstituted cyclopentane, in the 4-position it does have an effect on 1,2-substituted compounds, via the 1,2-dihedral angle. Thus, a 4-t-butyl group decreased the rate of cyclization of 2-benzoylaminocyclopentanol methanesulphonate to the corresponding oxazoline and also the rate of isomerization of cis- to trons-2-hydroxycyclopentanecarboxylic acid. 

A number of stereoselective syntheses of guaianolides have been based on the masked 3-hydroxycyclopentanecarboxylic acid (64) prepared from (S)-carvone (59) as illustrated in Scheme 98.8 [20]. 

The hydroxycyclopentanecarboxylic acid 64 has been used as starting material for enantiomeric pure guaianolides like (—)-estafiatin, thapsigargin (11) [20], and (+)-cladantholide (65, Scheme 98.9) [21]. Formation of the tricyclic ring... 

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