Of nagilactone

The methanolic extract of the leaves of P. gracilior (Kenya) caused mortality within 12 days after incorporation into a meridic artificial diet of several lepidopterous pest species. The toxic and growth inhibitory action of nagilactones C (3), D (4) and F (55) and podolide (39) towards these species are shown in Table 7. All tested podolactones are relatively potent growth inhibitors (ED50 4-30 ppm), while the concentration of the compounds that cause mortality was about two orders of magnitude... 

Table 7. Activities of nagilactones C, D and F and podolide towards different lepidopterous agricultural pest species.

In spite of the aforementioned results, the Ohmae group, which has carried out exhaustive studies on the content in nagilactones in forests where P. nagi grows, questions the allelopathic effects of nagilactones [77]. 

In the earlier studies on the chemical reactivity of podolactones, it was noticed that some standard chemical transformations were reported to lead to unexpected results. Some of these outcomes were found in the treatment of nagilactone A (1) and its diacetate (116) with chromic acid and sodium borohydride, respectively [17] (Scheme 4). 

The very same kind of transformation was found upon treatment of nagilactone C-7 acetate with sodium borohydride [57]. Both transformations supposes the first interconversion from type A to type C podolactone groups. In this sense, the particularly limited availability of... 

The first synthesis of nagilactone F was carried out by Hayashi et al. [83] starting from (+)-0-methylpodocarpic acid 158 in 23 steps (2% overall yield). The main characteristics of this synthesis include the transformation of the aromatic ring into the 5-lactone ring, the a arrangement (equatorial) of the isopropyl group by photochemical cyclization, as well as the construction of the y-lactone using radical conditions (Scheme 14). 

The same strategy used by Barrero et al. for synthesis of the fungic metabolite LL-Z1271a (63) was used to synthesize nagilactone F (55). Thus, starting from the mixture of communic acids, lactol 99 is achieved, an immediate precursor of both 55 and epimer 165, which are obtained by treatment with isopropylmagnesium bromide. Thus, the synthesis of nagilactone F (55) is completed, with an overall yield of 10%. (Scheme 15). 

Structures of nagilactone E and F, and biological activity of nagilactones as plant growth regulator. Hayashi, Y. Yokoi, J. Watanabe, Y. Sakan, T. Masuda, Y. Yamamoto, R. Chem. Lett. 1972, 9,759-762. 

Total synthesis of nagilactone F, a biologically active norditerpenoid dilactone isolated from Podocarpus nagi. Hayashi, Y. Matsumoto, T. Nishizawa, M. Togami, M. Hyono, T. Nishikawa, N. Uemura, M. J. Org. Chem. 1982, 47, 3428-3433. 

Enantioselective synthesis of nagilactone F via vinylsilane-terminated cationic cyclization. Burke, S.D. Kort, M.E. Strickland, S.MS. Organ, H.M. Silks, L.A., III. Tetrahedron Lett. 1994,35,1503-1506. 

As a first approach to the synthesis of nagilactone 296, a norditer-penoid isolated from Podocarpaceae, which inhibit the expansion and mitosis of plant cells, an intramolecular Diels-Alder reaction of allene 1,3-dicarboxylic acid esters was used. The cyclization of 297 afforded the 8-lactone 298, rather than the y-lactone 299 [85JCS(P1)747]. 

Ponolactone A and its glucoside are inhibitors of expansion and mitosis in plant cells. Ponolactone A was isolated from Podocarpus nakai and shown to have the structure (25) by a detailed study of its n.m.r. spectrum, utilizing the nuclear Overhauser effect. The C-14 epimer was prepared from the C-7 acetate of nagilactone. Inumakilactone B was isolated" from Podocarpus macrophyllus and shown by a combination of chemical and spectroscopic evidence to have the structure (26). Inumakilactone C was tentatively assigned structure (27) on the basis of spectroscopic evidence. 

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