Of podolactones

Podolactones are considered to be a group of natural products whose basic skeleton contains a y-lactone between carbons 19-6 and a 6-lactone between carbons 12-14, which are their characteristic functions Fig. (1) [1]. The numbering of the podolactone skeleton has been assigned on the basis of the totarane skeleton from which most of podolactones have been proposed to be derived. 

Appearance of podolactones in the extracts of Podocarpus species along with various derivatives with a totarane skeleton (totarol, 12-... 

BIOLOGICAL ACTIVITY OF PODOLACTONES Anti-tumoral Activity, a) Yoshida Sarcoma. 

Tnble 4. Antifungal activity of podolactones alone or in combination with V4 MIC of anethol... 

The studies on the inhibitory effects of podolactones A (29) and E (51) and nagilactone E (36) were extended to a range of bioassays [73]. In some of these assays, the effects of the podolactones were compared to those of lycoricidinol and harringtonolide, plant growth inhibitors (Table... 

Table 9. Concentration of podolactones and related compounds causing significant (P = 0.05) inhibition...

The aforementioned capability of podolactones to inhibit or stimulate plant growth was again verified in a study carried out by Macias and Barrero s groups [14]. In this study the allelopathic activity of 11 natural... 

Before the work reported by Hayashi s group in 1982 [21], the study of podolactones reactivities was limited to the preparation of analogs to facilitate their structure determination. This limited study of reactivity could be explained considering the poor content of podolactones in their natural sources. 

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 main drawback of the first method described by Barrero et al. [14] for the synthesis of podolactones, lies in the presence of a mixture of three isomers called communic acids (153), which requires a chromatographic separation over silicagel impregnated with 20% silver nitrate to eliminate mirceo-communic acid to allow use of the 2-component mixture of cis- and trans-isomers as starting material. Furthermore, some steps in this former synthetic strategy, such as the closure of the 6-lactone or the formation of the dienolide system need improvement. 

Plant growth inhibitory lactones from Podocarpus neriifolius. Structure of podolactone E. Galbraith, M.N. Horn, D.H.S. Sasse, J.M. Experientia 1972, 28, 253-254. 

Miller, G. W., Sasse, J. M., Lovelace, C. J. and Rowan, K. S., 1984. Effects of podolactone-type inhibitors and abscisic acid on chlorophyll biosynthesis in barley leaves. Plant Cell Physiol. 25, 635-642... 

Paleg, L. G., and Buta, J. G. 1982. Some physiological effects of podolactone-type inhibitors. Physiol. Plant. 55, 51-59... 

Sasse, J. M., Cerana, R., and Colombo, R. 1984. The effects of podolactone-type inhibitors on fuscicoccin-induced growth and proton efflux. Physiol. Plant. 62, 303-308... 

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