P.S. Kalsi

Stereostructures of inunal and isoalloalantolactone, two biologically active sesquiterpene lactones from Inula racemosa

Abstract Two new sesquiterpene lactones, inunal and isoalloalantolactone, have been isolated from Inula racemosa . Inunal, an aldehydolactone, displays considerable biological activity as a plant growth regulator. Structures have been assigned to these compounds on the basis of spectral data and chemical correlation with alantolactone and isotelekin.

Guaianolides from Saussurea lappa

Two new sesquiterpene lactones with an α,β-unsaturated aldehyde group have been isolated from the roots of Saussurea lappa. Their stereostructures have been established by the combined use of spectroscopic as well as chemical methods via their synthesis from dehydrocostus lactone.

Terpenoid lactones as plant growth regulators

Abstract Plant growth regulating activity of dehydrocostus lactone possessing an α-methylene-γ-lactone moiety has been compared with its two derived C-16 lactones, in which a trisubstituted double bond and a cyclopropane ring are conjugated with the lactone carbonyl. The results show that the two latter compounds are slightly more active than dehydrocostus lactone.

Structure and plant growth activity relationship in terpenoid lactones

Abstract In order to obtain structure—biological activity data the synthesis of 15 new terpenoid lactones from germacranolides, eudesmanolides, guaianolides and elemanolides was undertaken. These and 15 other compounds were then tested as plant growth regulators. These studies established that the biological activity associated with the α-methylene-γ-lactone moiety in a terpenoid lactone is further enhanced when a cyclopropane ring is placed in the α,β-position to the lactone carbonyl. No exception to this structure—activity data has been noted so far. Significantly, this activity is increased when a trisubstituted (Z)-double bond is in the position of conjugation and the only exception to this is (Z)-C13-methyl dehydrosaussurea lactone which is only as active as water. Almost always a C-4 epoxy, or a C-4, C-10 ether group in the guaianolide systems further enhances the biological activity associated with the parent lactone. A similar effect of the epoxy group is not observed in the case of eudesmanolides.

Biomimetic synthesis of 2,3-dioxabicyclo [4,4,0] decanes as plant growth regulators

Abstract Naturally occurring derivatives of 2,3-dioxabicyclo [4,4,0] decane from Ecucalyptus grandis have been reported to possess a wide range of biological control in various plants including the parent one. The biogenetic type synthesis of these compounds have been discussed in this Paper.

Three oxygenated alantolides from Inula racemosa

Abstract Three oxygenated alantolides have been isolated from Inula racemosa . Two of these are epoxyalantolides while the third is perhydroxy derivative. Stereostructures have been assigned to these compounds on the basis of spectral data and chemical correlation.

Carota-1,4-β-oxide, a sesquiterpene from Daucus carota

Abstract A new sesquiterpene ether, carota-1,4-β-oxide, has been isolated from the essential oil of the seeds of carrot 1 ( Daucus carota ). The structure and stereochemistry of this compound have been established by spectroscopic and chemical methods by its synthesis from carotol.

A dramatic effect of stereochemistry on the plant growth activity of the cadinane group of terpenoids

Abstract Seven cadinane terpenoids have been tested as plant growth regulators. Khusinoloxide and epikhusinol acetate greatly stimulated root initiation with hypocotyl cuttings of Phaseolus aureus seedlings.

Epoxy alantolides: Isoinunal—a new potent plant growth regulator from Inula racemosa

Abstract An investigation of Inula racemosa roots afforded, in addition to known sesquiterpene lactones, four new lactones with close biogenetic relationships. Their structures have been elucidated using spectral data and chemical correlation. The most interesting of these is isoinunal which is a potent root initiator with hypocotyl cuttings of Phaseolus aureus .

Plant growth activity of guaianolides with C-4 oxygen-containing groups

Abstract The plant growth activity of guaianolides with C-4 oxygen-containing functions has been studied. It was found that the presence of an epoxy or an ether link at C-4 enhanced the plant growth activity of the parent compound. The presence of a hydroxyl group at C-4 had no effect.