Prostanoic acid, structure

In parallel with these experiments, studies on the mechanism of formation of TXBj were carried out [19]. It appeared conceivable that more than one reaction would be needed for the formation of the non-prostanoic acid structure of TXB2 from PGG2/PGH2. An attractive sequence of reactions consisted of enzymatic formation of a bicyclic oxetane-oxane derivative followed by non-enzymatic hydrolysis of the oxetane ring to yield TXB2. In order to test this possibility, short time incubations (30-60 s) of arachidonic acid with platelets were carried out. The... 

The prostaglandins (qv) constitute another class of fatty acids with aUcycHc structures. These are of great biological importance and are formed by i vivo oxidation of 20-carbon polyunsaturated fatty acids, particularly arachidonic acid [27400-91-5]. Several prostaglandins, eg, PGE [745-65-3] have different degrees of unsaturation and oxidation when compared to the parent compound, prostanoic acid [25151 -18-9]. 

The prostaglandins are a group of naturally occurring compounds whose molecular structures are based on that of prostanoic acid. 

Figure 16.23 Structure of prostanoic acid and the cyclopentane ring of prostaglandins A through I a and indicate the orientation of the 9-hydroxy group.

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. 

Figure 1 shows the basic carbon structures for these two classes of substances. All steroids contain the perhydrocyclopentanophenanthrene ring system while the carbon skeleton basic to all prostaglandins has been called prostanoic acid. The steroid hormones are discussed first. 

The prostaglandins prostacyclin and thromboxane, collectively termed prostanoids, can be considered analogs of unnatural compounds with the trivial names prostanoic acid and thrombanoic acid, with the structures shown below ... 

Following the publication in 1966 of the first route to a biologically active prostaglandin [115], many total chemical syntheses of the natural prostaglandins and their structural variants have been reported. Here syntheses of the four main groups—PGE, F, A and B—and their unnatural stereoisomers are discussed first, followed by an account of routes to dihydroprostaglandins and novel derivatives of prostanoic acid. See also note on p. 366. 

Fig. I. (a) The structure of prostanoic acid, the carbon skeleton of the prostaglandins, and the structure and functional groups of the cyclopentane ring in prostaglandins A to I. (b) Structures of prostaglandins E, E2 and the first prostaglandins to be identified (cf. refs. 6. 7).

Prostaglandins are also classified by the functional groups of the cyclopentane ring. The systematic nomenclature from prostanoic acid is straightforward, but for practical reasons the non-systematic use of capital letters to denote the ring substituents has become widely accepted. The structures of the cyclopentane ring... 

Prostaglandins are oxygenated polyunsaturated carboxylic acids that contain a five-membered ring. They may be considered chemically as derivatives of the theoretical parent compound prostanoic acid (Figure 1) and their nomenclature is based on this structure. 

Prostaglandins are a group of molecules based upon the 20-carbon structure of prostanoic acid, which is a fatty acid containing... 

FIG. 1. Molecular structures of 9 hydroxy-19,2Q-bis--nor-prostanoic acid (sodium salt) and. ... 

The loss of one carbon atom of the side chain is an uncommon degradation. Further studies with tritium labelled compound to determine the excretion and distribution of this compound in several animal species are now in progress, as are studies to fully determine the metabolic pathway of 9-hydroxy-19,20-bis--nor prostanoic acid and to confirm the structure proposed for all unknown metabolites. 

Pio. 1. Structures of one group of naturally occurring prostaglandins with abbreviated names and chemical names based on the parent acid, prostanoic acid. 

Figure 6.60 Prostaglandins are derivatives of prostanoic acid. Numbering begins at the acid and continues around the entire structure. Note the frans-substituents on the cyclopentane ring with the absolute stereochemistry as shown.

Prostaglandins, PG a group of biologically active unsaturated C20 fatty acids derived primarily from Arachidonic acid (see). The PG are related structurally and metabolically to the Letrkotrienes (see) and Thromboxanes (see). All PG can be consider as formal derivatives of prostanoic add (which does not occur naturally). The conventional abbreviation is PG, with an additional letter and number. The E series are p-hydroxyketones, the F series are 1,3-diols the A type are a,P-unsaturated ketones. All PG have a double bond at C13 and an OH group at CIS. The series number indicates the number of double bonds, which depends on the fatty acid precursor. Series 1 are biosynthesized from 8,11,14-eicosatrienoic acid, series 2 from arachidonic add, and series 3 from 5,8,11,14,17-eicosapentaenoic add. Series 2 compounds are most abundant. Some PG have little or no biological activity and are presumably metabolic products of the active spedes. The active species are... 

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