Ring D-modified gibberellin compounds, and preparation and use t

Details Ring D-modified gibberellin compounds, and preparation and use t Ring D-modified gibberellin compounds, and preparation and use t

1997-05-08

1998-06-16

Owens, Amelia

Plant protecting and regulating compositions

Plant growth regulating compositions

Organic active compound containing

549298, 549299, C07D30777

Patent

active

057670420

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/AU95/00528 filed Aug. 25, 1995.
This invention relates to ring D-modified gibberellin compounds, to processes for the production thereof, and to methods of use of these compounds.
As disclosed in prior International Patent Application No. PCT/AU92/00426 (WO 93/03616), numerous phytoactive substances are known, including the C-16,17-dihydro gibberellins, which can be used in agricultural and horticultural practice in order to promote desired physiological effects in higher plants. Such effects include promotion of flowering, inhibition of flowering, inhibition of seed head formation, weed control, inhibition of stem elongation (dwarfing), improvement of hardiness, promotion of rooting and inhibition of root or shoot growth in germinating seeds. Unfortunately, most available phytoactive substances have undesirable side effects and may give rise to toxic residues which tend to pollute the environment.
Gibberellins (GAs) are known to influence both growth and flowering in many plants, particularly in those requiring exposure to long days for flowering (Lang, 1965; Zeevaart, 1983; Pharis & King, 1985). The grass Lolium temulentum is such a long day (LD) plant (Evans, 1964, 1969), and recent studies with that species have revealed quite different structural requirements for the promotion of stem elongation on the one hand and floral inflorescence initiation on the other (Evans et al., 1990). The different structural requirements of these two processes were even more apparent in experiments with C-16,17 dihydro derivatives of several GAs, especially of GA.sub.5 and GA.sub.20, where at optimal doses they promoted flowering, but inhibited stem elongation by up to 40% (Evans et al., 1994b). Such a combination of effects also is of horticultural significance. Additionally, it has also been reported that the C-16,17-dihydro gibberellins can reduce leaf and leaf sheath elongation in rice (Takagi et al., 1994).
At doses which gave good inhibition of stem elongation, flowering of Lolium was not inhibited by C-16,17-dihydro gibberellins (Evans et al., 1994b) and could be promoted both by these gibberellins and by the gibberellin biosynthesis inhibitor CGA 163935. As found with CGA 163935 (Adams et al., 1992), these C-16,17-dihydro gibberellins apparently act to block late steps in gibberellin biosynthesis (Takagi et al., 1994).
Suppression of turfgrass by various growth retarding chemicals has been widely reported both for warm- and cool-season grass mixtures (Kaufman, 1990). However, responses have not always been consistent, yellowing may result (Sander and Hensley, 1993) and the growth retardant used may not be environmentally acceptable. The type of growth suppression varies with the chemical used, maleic hydrazide and mefluidide causing shoot mortality with rapid proliferation of new shoots whilst flurprimidol and paclobutrazol only suppress foliar growth (Spak et al., 1993). Seedhead suppression is also desirable and Johnson (1990, 1993) reported beneficial responses with imazethapyn, mefluidide and prinexapacethyl (Primo.TM. or CGA 163935) on centipede grass. In the case of CGA 163935, high doses were required and this led to foliar damage.
The objective in many turf management situations is to maintain a dense turf with active photosynthesis, leaf formation and tillering but with reduced leaf elongation and prevention of inflorescence formation. Repeated mowing is an expensive--and sometime hazardous--solution, and a compound which reduces stem and leaf elongation without reducing photosynthesis, leaf appearance rate, leaf longevity and plant viability is highly desirable.
Prior International Application No. PCT/AU92/00426 discloses a method of treatment comprising the application to a plant or to plant tissues (including cuttings, roots, bulbs, corms, tubers, rhizomes and seeds) of a C-16,17-dihydro gibberellin or a C-16,17-dihydro gibberellin precursor effective to produce an at least partial inhibition of the formation of effector gibberellins that cause growth and development i

REFERENCES:
March, J. Adv. Org Chem (1977) p. 794.

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