Cyclopentanoid monoterpenes

Harney JW, Barofsky IM, Leary JD. (1978). Behavioral and toxicological studies of cyclopentanoid monoterpenes from Nepeta cataria. Lloydia. 41(4) 367-74. 

In the cyclopentanoid monoterpene family, compounds containing an iridoid-structure exhibit various bioactivities in Nature. For example, dehydroiridodiol, isolated from dry leaves of the cat-attracting plant Actinidia polygama Miq., is known to be an attractant for the male adults of the Chrysopidae and shows activity in amounts as small as lO"" pg [35]. Dehydroiridodial, a more oxidized product, was isolated as a pungent principle of Actinidia polygama Miq. and was characterized by T. Sakan et al. in 1978 [36]. 

Thomas (23) predicted that the non-tryptamine moiety of the indole alkaloids is derived from a cyclopentanoid monoterpene precursor. Wenkert (2k) independently reached to the same conclusion. 

Cavill and his co-workers have reported stereospecific syntheses of the enantiomers of two naturally occurring cyclopentanoid monoterpenes, iridodial and nepeta-lactone, from the common precursor D-(+)-pulegone 219, Scheme 35).299 ... 

The previous examples rehed on a radical termination. Cationic termination could also be used, after suitable oxidation of the final radical (Scheme 75) [211]. Thus, ester 252 was treated with base and ethylchloro-formate to give anion 253, which was oxidized to malonyl radical 254 by the ferrocenium ion. Cyclization/oxidation gave cation 256, which yielded 93% of malonate 257 by loss of the TMS group. This adduct was further elaborated upon and led to a cyclopentanoid monoterpene, dihydronepetal-actone. 

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. 

Iridoids. Iridoids are cyclopentanoid monoterpenes that occur widely as glucosides. The first synthesis of an iridoid glucoside, loganin (4), was achieved by Biichi et al The key step involved photoannelation of 1 to the tetrahydropyranyl ether of 3-eyclopentenol (2), which resulted mainly in 3. Remaining steps to 4... 

Morota T, Nishimura H, Sakai H, Chin H, Sugama K, Karsuhara T, Mitsuhashi H (1989) Five cyclopentanoid monoterpenes from Rehmannia glutinosa. Phytochemistry 28 2385-2391... 

Cyclopentanoid monoterpenes (contd.) nepetic and nepetalinic acids. 

Cavill, G. W. K. The cyclopentanoid monoterpenes. Rev. Pure Appl. Chem, 10, 169... 

Tallent, W. H. Two new antibiotic cyclopentanoid monoterpenes of plant origin. Tetrahedron 20, 178I (1964). 

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