Other Cyclopentanoids

Clinical success with the monoamine oxidase inhibitor and amphetamine analogue tranylcypromine (27) led to 

Clotting of blood is, of course, one of the more significant ways in which the body protects itself from excessive blood loss after injury. 

After the healing takes place, the clot, which is a three-dimensional polypeptide, is broken down by proteolytic enzymes such as fibrinolysin or plasmin. 

In some pathological states, fibrinolysis is hyperactive and inhibitors have a hemostatic value. 

Plasmin does not occur in free form but is generated as needed from an inactive precursor, plasminogen. The active of plasminogen to plasmin is a proteolytic event and can be inhibited by ut- 

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Generation of the endocyclic double bond of cyclopentanoids has been accomplished frequently by rDA reaction of the appropriate cyclopentadiene. FVP has been used as the last step of the synthesis of the antibiotic ( )-pentenomycin (53) in 50% yield. " Other cyclopentanoid natural products that are synthesized by procedures based upon a nearly quantitative rDA reaction are jasmone (54) and alkyne (55), a precursor to methyl jasmonate. This same procedure has been applied to the synthesis of intermediates of prostaglandins such as (56). ... 

Hydroacylation is especially interesting in its intramolecular version, converting unsaturated aldehydes to cyclopentanones. Numerous examples of transition metal catalyzed hydroacylations have been described, mostly with 4-alkenals of various substitution patterns. The reaction is used for the construction of starting materials in prostaglandin synthesis and the preparation of other cyclopentanoid systems. Rhodium catalysts, mainly of the Wilkinson type, are used. The steric course of hydroacylation is believed to occur in a m-addition manner. This was deduced from results of intermolecular alkyne hydroacylation56 (vide supra) and the intramolecular hydroacylation of deuterated E- and Z-isomers of 7,5-unsaturated aldehydes39-5 . 

Tetrahydrofurans (and other cyclopentanoids) have been obtained by a methylmanganese pentacarbonyl mediated transformation of enynes <97TL1781>. A variety of cw-2-substituted... 

This chemistry has been applied to the synthesis of intermediates to muconic esters [38], hydrazulene derivatives [39], and a number of other cyclopentanoid or cycloheptanoid compounds [40]. The chemoselectivlty of the reaction could be improved by the presence of a phenylsulfanyl substituent at the double bond in 33 [41], and the diastereoselectivity has been investigated in the context... 

The synthesis of other angularly fused triquinanes as well as linearly fused sesquiterpenes such as hirsutene and capnellene quickly followed. Many general methods for the synthesis of cyclopentanoid natural products emerged as a result of the target-oriented effort [6]. These accomplishments have been reviewed extensively on numerous occasions [7]. This chapter reviews the history of retigeranic acid from its isolation and structure determination to published approaches to its synthesis and the four total syntheses accomplished to date. 

Khand annulations (extremely efficient in the synthesis of polyquinanes and cyclopentanoid sesquiterpenes -triquinacene, coriolin, etc.-, among many others). 

Secologanin (1) of Fig. (1) is the most important representative of the iridoids (la), a special type of cyclopentanoid monoterpenes. (1) belongs the subclass of secoiridoids (lb), in which the bond C-7-C-8 is cleaved [1]. The number of known iridoids is more than 650 [2], The biosynthesis of iridoids like that of other monoterpenes starts from two C5 units (lc) whose precursor was considered to be mevalolactone [3], However, recently it was proved that the biosynthesis of some classes of terpenoids [4,5], and specially of secologanin [6] runned from 1-deoxy-D-xylulose-5-phosphate as an alternative or even main route. 

These optically active cyclopentanoids have been synthesized from tartaric acids or their derivatives employing a new phosphonate-based strategy for the construction of substituted cycloalkenones. Therefore, before presenting total syntheses of terreins it is desirable to outline this new strategy because it was used in the synthesis of other bioactive products. It was found [33, 34] that 3-(phosphorylmethyl)-2-cycloalkenones 23 are formed in good yields by intramolecular Horner-Wittig reaction of the corresponding bis- -ketophos-phonates which, in turn, are easily prepared from dicarboxylic acid esters and a-phosphonate carbanions (Scheme 10). 

Prostaglandin One of a class of lipid hormones containing 20 carbons, 5 of which belong to an oxygenated cyclopentanoid ring the remaining 15 carbons are incorporated into two unbranched side chains, adjacent to each other on the ring. 

Many metabolically altered triterpenes contain epoxides, lactones, furans, and cyclopentanoid systems, functional units that are associated with biological activity in other... 

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