Fatty acids cyclopentane

The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxyUc acids present in cmde oil. Naphthenic acids [1338-24-5] are classified as monobasic carboxyUc acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentane and cyclohexane derivatives. Naphthenic acids are composed predorninandy of aLkyl-substituted cycloaUphatic carboxyUc acids, with smaller amounts of acycHc aUphatic (paraffinic or fatty) acids. Aromatic, olefinic, hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic acids also contain varying amounts of unsaponifiable hydrocarbons, phenoHc compounds, sulfur compounds, and water. The complex mixture of acids is derived from straight-mn distillates of petroleum, mosdy from kerosene and diesel fractions (see Petroleum). 

In addition to unsaturated fatty acids, several other modified fatty acids are found in nature. Microorganisms, for example, often contain branched-chain fatty acids, such as tuberculostearic acid (Figure 8.2). When these fatty acids are incorporated in membranes, the methyl group constitutes a local structural perturbation in a manner similar to the double bonds in unsaturated fatty acids (see Chapter 9). Some bacteria also synthesize fatty acids containing cyclic structures such as cyclopropane, cyclopropene, and even cyclopentane rings. 

Figure 11.26 The structures of the prostaglandin E series produced from three polyunsaturated fatty acids containing 20 carbon atoms but a different number of double bonds. The number of double bonds in the three different acids produces prostaglandins of the E series with a different number of double bonds outside the cyclopentane ring. It is this number which influences the function of the prostaglandin and similarly the function of prostacyclins and thromboxanes (see text). Note, PGEi has one double bond, PGE2 has two double bonds and PGE3 has three double bonds outside the cyclopentane ring.

Some of the most recent and exciting developments in the field of natural products are related to the compounds known as prostaglandins. All are oxygenated unsaturated derivatives of prostanoic acid, which is a C20 fatty acid in which there is a cyclopentane ring formed by connecting the C8 and Cl2 positions ... 

Prostaglandins are cyclopentane derivatives of unsaturated C20-fatty acids. They display hormonal as well as regulatory activities and were detected for the first time in spermatic fluid. They are obviously widely spread in animal tissue. Biosynthesis of prostaglandins involves cyclization of polyunsaturated carboxylic acids, e.g. arachidonic acid [(5Z,8Z,llZ,14Z)-5,8,ll,14-eicosatetraenoic acid] is enzymatically converted directly into prostaglandin PGE2. Prostaglandins stimulate and contract certain smooth muscles. At very low concentrations they lower the blood pressure and influence the heart frequency. Some of them can release labour and... 

Goda et al. (1995) separated capsanthin esters from oleoresin of paprika fruits from Spain and determined their chemical structures without saponification. The major monoesterified capsanthin was identified as 3 -0-myristoylcapsanthin. It is suggested that the rate of esterification of fatty acid to the hydroxyl group on the cyclopentane ring of capsanthin is different to that on the cyclohexene ring. 

PGs of the 1 series have a trans double bond in the An position, whereas PGs of the 2 and 3 series have an additional cis double bond at A5, and additional cis double bonds at both A5 and A17, respectively. PGs are also classified by the functional groups attached to the cyclopentane ring, denoted A through I (Figure 16.23). TXs and PGIs are closely related to the PGs and can be of the 1, 2, or 3 series, depending on the fatty acid from which they are derived. 

The standard nomenclature for this family of readily released fatty acids from tissues and organs and the synthetic prostaglandin-like compounds is derived from the C-20 cyclopentane acid skeleton of the hypothetical prostanoic acid 1. 

The numbering of the carbon atoms is, according to the nomenclature rules used by the Chemical Abstracts7, 8, consistent with the numbering for fatty acids. The compounds are typed depending upon the substitution pattern of the cyclopentane ring and classified by the degree of unsaturation in the side chains see Scheme 1. 

The prostaglandins are a series of C20 unsaturated fatty acids containing a cyclopentane ring the parent fatty acid... 

Prostaglandins (PG) were discovered in human semen more than 50 years ago. Their name derives from the prostate gland, but they are produced in many tissues. In fact, the high concentrations found in semen arise in the seminal vesicles rather than the prostate. The chemical parent compound is a 20 carbon unnatural fatty acid known as prostanoic acid that contains a five-membered (cyclopentane) ring. Derivatives that contain this structure (PGs, TXs, and PGIs) are known collectively as prostanoids. 

The fungus Gibberella fujikuroi produces the gibberellins and the pigment bikhaverin. Some strains also produce the fusarins, e.g. 4.101, and fumanosins, e.g. 4.102, which are serious mycotoxins and phytotoxins. Cyclopentane fatty acids of the jasmonic acid type such as V-jasmonyl isoleucine (4.103) and its dihydro derivative have also been isolated from Gibberella fujikuroi. 

Brefeldins A (4.104) and B, obtained from Penicillium brefeldianum and which also possess a cyclopentane ring, have a wide spectrum of biological activity, including antiviral and cytotoxic effects. Brefeldin A has been shown to incorporate acetate and specifically [9- C]palmitic acid, suggesting that it is biosynthesized by a fatty acid pathway. However, other macrolactones such as curvularin appear to be biosynthesized by a polyketide pathway. 

Jasmonic acid (1) and its related compounds which are classified as cyclopentane fatty acids are distributed widely in higher plants [1] and in some micro-organisms [2] (Fig. 1). 

Prostaglandins are fatty acids of 20 carbon atoms having a cyclopentane ring with two adjacent side chains. Their chemical structure was elucidated in the early 1960s as a result of ultramicroanalysis and mass spectrometry together with various degradations of the small amounts of material then available [18]. A detailed review of the methods used has been published by Samuelsson [19]. The absolute stereochemistry was finally decided upon in 1966 [20] some papers published before then show the side chains in the positions now known to represent the mirror image of the natural forms. 

Several important metabolites of polyunsaturated fatty acids (PUFA) contain a cyclopentane ring. Compounds such as jasmonic acid, cucurbic acid, and tuberonic... 

Fig. 1 Structures of various CD complexes. Toluene fits well into a (3CD cavity, for diphenylamine, two (3CDs form a "capsule. A long-chain fatty acid can take up three or more aCDs. A short-chain fatty acid and diethylether form a stable ternary complex. In the case of prostaglandin E, the otCD accomodates only the aliphatic chain of the unsaturated cyclic hydroxy-fatty acid, but it is enough to convert it into a water-soluble complex. The pCD can accomodate the cyclopentane moiety, but /CD is too wide for this guest. (Wen-this art in color, at www.dekker.com.)...

Prostaglandins are cyclopentane derivatives (Section 1.4) formed from poljomsaturated fatty acids by most mammalian tissues (and by tissues of lower vertebrates and certain invertebrates). These prostaglandins modulate a host of hormonal, neurohormonal and other stimuli and have a variety of other pharmacological actions (Samuelsson et aL, 1975, 1978). Thromboxanes themselves are of pronounced biological activity but are unstable with short half-lives (cf. Samuelsson etal., 1978). 

Prostaglandins have 20 carbon atoms. They are synthesized in the body by oxidation and cyclization of the 20-carbon unsaturated fatty acid arachidonic acid. Carbon-8 through carbon-12 of the chain are looped to form a cyclopentane ring, and an oxygen function (carbonyl or hydroxyl group) is always present at carbon-9. Various numbers of double bonds or hydroxyl groups may also be present elsewhere in the structure. 

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