Cyclopentanoic acid

The application of this addition to aminomethylene ketones provides a convenient synthesis of monoamides of pimelic acid (508). It should be noted that the corresponding oxidation of hydroxy methylene cyclohexanone leads to ring contraction and formation of cyclopentanoic acid. 

All prostaglandins are cyclopentanoic acids derived from arachidonic acid. The biosynthesis of prostaglandins is initiated by an enzyme associated with the endoplasmic reticulum, called prostaglandin endoperoxide synthase, also known as cyclooxygenase. The enzyme catalyzes simultaneous oxidation and cyclization of arachidonic acid. The enzyme is viewed as having two distinct activities, cyclooxygenase and peroxidase, as shown in Figure 25.28. 

Synthesis. Both the cyclopentanoate drum composition, 3, and the cyclohexanoate drum, [n-BuSn(0)02CC6Hi1]g>, A> were prepared by a condensation reaction of n-butyl stannoic acid with the corresponding carboxylic acid, Equation 1. 

The pyrolysis of lead salts of dicarboxylic acids gives ketones, as exemplified by the formation of 2-methyl-2-cyclopentano[4,3-d]thiazol-5-one (equation 16) (63JPR(292)285). 

No or only minimal cytotoxicity of most coumarins could be detected in normal cells in contrast to the positive control gallic acid. On the other hand, several of them showed concentration-dependent cytotoxicity against tumor cell lines HSC-2 and HSC-3. Among them, 6-hydroxy-7-methoxycoumarin derivatives (C29, C30, C39, C40, C41, C42, and C43) were cytotoxic to tumor cell fine HSC-2. However, C34 and C38 were relatively non-toxic to all cell lines used. It is suggested that the presence of polar substituents such as ester and alcohol group at the C-3 and/or C-4 position was unfavorable for cytotoxicity. This observation confirms the recent findings that 3,4-dimethyl- (C17) and 3,4-cyclopentano-6-hydroxy-7-methoxycoumarin (C22) showed marked cytotoxic effects [25]. However, it should be noted that 4-methyl-6-hydroxy-... 

The dihydro-cyclopentano-phenanthrene (120) has been synthesized (Scheme 9) from 2-acetyl-3-methylnaphthalene (115), which was converted into the fur-furylidene derivative (116). Treatment with acid afforded the expected dioxo-heptanoic acid (117), which on treatment with base provided the cyclopentenone (118). This keto-acid (118) readily underwent cyclization when boiled with acetic anhydride, furnishing ll-acetoxy-15,16-dihydro-7-methylcyclopenta[a]-phenanthren-17-one (119a). Deoxygenation at C(ll) was performed through... 

The Hudlicky route making vinylcyclopropanes by intramolecular car bene additions to dienes has led to a variety of polycyclic cyclopentanoic terpenes. The crucial step in a synthesis of isocomenic acid is illustrated by equation 157. ... 

A soln. of startg. epoxyketone in chloroform treated with 2 eqs. benzoic acid at room temp, for 30 h - product. Y 87.4%. The method is applicable to highly functionalized cyclopentano- and cyclohexano-analogs. E.s. T. Suzuki et al.. Heterocycles 27, 21-4 (1988). 

Not just limited to five-membered rings, the intramolecular Houben-Hoesch can be used to form rings of various sizes. The Patterson group synthesized cyclopentano, cyclohexano, and cycloheptano[a]pyrroles under Houben-Hoesch conditions using the Lewis acid Bp3-OEt2 followed by a... 

Two classes are recognized, the so-called neutral saponins (digitalis saponins), which have as aglycons substances derived from cyclopentano-perhydrophenanthrene, and the acid saponins, which have as aglycons substances derived from triterpene. The aglycons are called sapogenins. Most of the investigations have been devoted to the determination of the structures of the neutral saponins. 

Crotonic acid anhydride 1454 Cyclopentanoic acid 2663 2 -Deoxy-5 -cytidylic acid 2801... 

Raney-Ni alloy added in small portions during 1.5 hrs. to a well-stirred soln. of -(2-oxocyclopentyl)butyric acid in aq. NaOH, and stirring continued 7 hrs. at room temp. -methyl-y,<5-cyclopentano-5-valerolactone (Y 98.9%) added at ca. 60° to polyphosphoric acid, and heated 5.5 hrs. at the temp, with occasional swirling under anhydrous conditions -> 4-methylbicyclo[3.3.0]-id 1.5-octen-2-one (Y 95.5%). Overall Y ca. 66%. F. e. s. T. M. Jacob and S. Dev, J. Indian Ghem. Soc. 36, 429 (1959). 

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