GB2127021A

GB2127021A - Brassinosteroid derivatives having a plant growth-regulating action and their manufacture and use

Info

Publication number: GB2127021A
Application number: GB08324347A
Authority: GB
Inventors: Ulrich Kerb; Ulrich Eder; Hansjorg Krahmer
Original assignee: Schering AG
Current assignee: Bayer Pharma AG
Priority date: 1982-09-15
Filing date: 1983-09-12
Publication date: 1984-04-04
Also published as: GR78759B; DK417783D0; JPS5955887A; KR840005736A; BR8304545A; AU1861283A; ES525035A0; FI833252A; ZA836872B; DE3234605A1; PT77257B; PL243719A1; BE897758A; IL69701A0; DK417783A; ES8404696A1; LU85002A1; SE8304841L; IT8322861A0; IT1194398B

Abstract

Novel brassinosteroid derivatives of the general formula I <IMAGE> (in which R17 represents C8-C10-alkyl or -alkenyl, Z represents -CO-O- CH2- or -O-CO-CH2-, and R2 and R3 each represents H or acyl or together represent <IMAGE> X representing H, optionally chlorinated C1-C4-alkyl or C1-C3- alkoxy and Y representing H, optionally chlorinated C1-C4-alkyl, C1-C3-alkoxy or optionally substituted aryl) and their manufacture. The novel compounds have a plant growth-regulating action, being particularly suitable for influencing the vegetative and generative growth of leguminous plants, for example soya bean plants, and accordingly may be made up with suitable carriers and/or auxiliaries into plant growth- regulating preparations and may be used for treating seeds, living plants and areas of land.

Description

SPECIFICATION Brassinosteroid derivatives having a plant growth-regulating action and their manufacture and use The present invention is concerned with novel brassinosteroid derivatives, with a process for the manufacture of these compounds and with their use as agents having a growth-regulatory effect on plants.

A steroid that promotes plants growth, namely brassinolide, has been isolated from the pollen of rape and its structure determined [see M. D. Grove etna!., Nature, vol. 281,216 (1979)]; it is (22 R,23R,24S)-2a,3 ,22,2 3-tetrahydroxy-24-methyí-6,7-s-5a-choíestano-6,7-íactone. The growthregulatory action of this compound is, however, not satisfactory.

The problem upon which the present invention is based has been to develop novel brassinosteroid derivatives that, in comparison with the known brassinolide of analogous constitution, have superior growth-regulatory properties for plants.

This problem is solved according to the present invention by the novel brassinosteroid derivatives, as defined below.

The present invention accordingly provides compounds of the general formula I

in which R,7 represents a C8-C10-alkyl group or a C8 < ,0-alkenyl group, Z represents a group of the formula

and R2 and R3 each represents a hydrogen atom or an acyl group or together represent a group of the formula

in which X represents a hydrogen atom, a C1-C4-alkyl group, a chlorinated C1-C4-alkyl group or a C1-C3-alkoxy group and Y represents a hydrogen atom, a C1-C4-alkyl group, a chlorinated C1-C4-alkyl group, a C1-C3- alkoxy group or an unsubstituted or substituted aryl group.

The compounds of the present invention occur as geometrical isomers, -OR2 and -OR3 being cis 2a,3a or cis 2P,3P oriented. Thus it is to be understood in the description and claims herein that when reference is made to a compound of the general formula I, such a compound may be in the form of such an individual isomer or of a mixture of the two isomers.

The compounds of the present invention are outstandingly suitable for regulating plant growth in various crop plants and are surprisingly superior in their range of action and also in their compatibility as compared with the product of the same direction of action, mentioned in the introduction above.

The compounds according to the present invention are capable of promoting the vegetative growth of crop plants and, in certain concentration ranges, also of inhibiting it. In addition, it is possible, by influencing the generative phase, to achieve certain multiple harvests.

In general, the compounds of the present invention act on the membrane system in crop plants and alter the permeability thereof to various substances.

Under certain conditions, they may exhibit an anti-stress action.

Since the compounds according to the present invention bring about both qualitative and quantitative changes in plants and also alter the metabolism of the plants, they are to be included in the class of plant growth regulators which are distinguished by the following possible applications: Inhibiting the vegetative growth in woody and herbaceous plants, for example inter alia on roadsides and railway tracks in order to suppress a growth that is too lush. Inhibiting growth in cereals in order to prevent lodging or snapping off, and in cotton to increase the yield.

Influencing the branching out of vegetative and generative organs in ornamental and crop plants in order to increase the amount of blossom, or in the case of tobacco and tomato plants to inhibit the formation of side shoots.

Improving the quality of the fruit, for example increasing the sugar content of sugar cane, sugar beet or fruit, and producing a more uniform ripening of the crop which results in higher yields.

Increasing the resistance to stress, for example to climatic effects, for example cold and drought, and also to the phytotoxic effects of chemicals.

Influencing the flow of latex in rubber plants.

The development of parthenocarpic fruits, pollen sterility and influencing of sex are likewise possible applications.

Controlling the germination of seeds or the production of buds.

Defoliating or influencing the fall of fruit to facilitate harvesting.

The compounds according to the present invention are particularly suitable for influencing the vegetative and generative growth in some leguminous plants, for example soya bean plants.

Depending on the purpose of application, the quantities applied are generally within the range of from 0.001 to 1 kg of active substance per hectare, but greater application quantities may also be used if appropriate. When two or more compounds of the present invention are used, the range of 0.001 to 1 kg per hectare refers of course to the total application quantities.

The time of application depends on the purpose of application and on the climatic conditions.

When used as agents for regulating the growth of plants, the compounds of the present invention may, if desired, be used in admixture with a suitable carrier and/or an auxiliary.

Of the compounds according to the present invention, those that are especially distinguished by the described action are the compounds of the general formula I in which R17 represents a 2-methyl-heptan-6-yl, 2-methyl-3-ethyl-hept-4-en-6-yl, 2,3-dimethyl-hept-4en-6-yl, 2-methyl-3-ethyl-heptan-6-yl or 2,3-dimethyl-heptan-6-yl group, represents a group of the formula Z represents a group of the formula

and R2 and R3 each represents a hydrogen atom, a formyl group, a C2-C7-alkyl-CO- group, a C2-C7-alkoxy-C1-C3-alkyl-CO- group, an aryl-CO-- group or an aryl-C1-C2-alkyl-CO- group, or together represent a group of the formula

As C8-C10-alkyl and -alkenyl groups represented by R17 in the general formula I there may be mentioned, for example, 2-methyl-heptan-6-yl, 2-methyl-3-ethyl-hept-4-en-6-yl, 2,3-dimethyl-hept-4en-6-yl, 2-methyl-3-ethyl-heptan-6-yl and 2,3-dimethyl-heptan-6-yl groups.

As acyl groups represented by each of the symbols R2 and R3 in the general formula I there may be mentioned, for example, a formyl group, a C2-C7-alkyl-CO- group, a C2-C7-alkoxy-C1-C3-alkyl- CO- group, an aryl-CO-- group and an aryl-C1-C2-alkyl-CO- group, for example acetyl, methoxyacetyl, ethoxyacetyl, propionyl, butyryl, valeryl, pentanoyl, hexanoyl, heptanoyl, dimethylacetyl, diethylacetyl, benzoyl and phenylacetyl.

As optionally chlorinated C1-C4-alkyl groups represented by the symbols X and Y there may be mentioned, for example, methyl, ethyl, propyl, isopropyl, butyl, sec.-butyl, tert.-butyl and chloromethyl; as C1-C3-alkoxy groups there may be mentioned, for example, methoxy, ethoxy and propoxy; as optionally substituted aryl groups there may be mentioned, for example, naphthyl, phenyl, 2 chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, 2,6-dichlorophenyl, 2,4-dichlorophenyl, 3,4dichlorophenyl, 2,4,6-trichlorophenyl, 4-bromophenyl, 2,4-dibromophenyl, 2,6-dibromophenyl, 2,4,6tribromophenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2 ,4-difluorophenyl, 2-methylphenyl, 3methylphenyl, 4-methylphenyl, 3,4-dimethylphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4methoxyphenyl, 3,4-dioxymethylenephenyl, 2-phenoxyphenyl, 3-phenoxyphenyl, 2-nitrophenyl and 3nitrophenyl.

The present invention accordingly also provides a preparation for regulating the growth of plants, which comprises at least one compound of the general formula I in admixture with an auxiliary.

The present invention further provides a preparation for regulating the growth of plants, which comprises at least one compound of the general formula I in admixture or conjunction with a suitable carrier.

The present invention further provides a method of regulating the growth of a living plant, wherein the living plant and/or the area in the vicinity of the living plant is/are treated with a compound of the general formula I.

The present invention further provides a method of regulating the growth of plants in an area of land, for example a crop area, wherein the area is treated with a compound of the general formula I.

The present invention further provides a method of dressing seeds, wherein the seeds are treated with a compound of the general formula I.

The present invention further provides a pack which comprises at least one compound of the general formula I, together with instructions for its use for regulating the growth of living plants.

The compounds according to the present invention may be applied singly or in the form of mixtures with each other or with other active substances. If desired, defoliants, plant-protecting agents and/or pesticides may be added, depending on the desired aim of application.

If a broadening of the range of action is intended, other biocides also may be added. For exmaple, as herbicidally active co-components there are suitable the active substances that are listed in Weed Abstracts, vol. 31, 1981, under the title "List of common names and Abbreviations employed for currently used herbicides and plant growth regulators in weed abstracts". In addition, it is also possible to use non-phytotoxic agents that are capable of producing with herbicides and/or growth regulators a synergistic increase in action, inter alia, for example, wetting agents, emulsifiers, solvents and oily additives.

The active compounds according to the present invention or mixtures thereof are advantageously applied in the form of preparations, for example powders, strewable preparations, granules, solutions, emulsions or suspensions, with the addition of liquid and/or solid vehicles or diluents and, if desired, of surface-active agents, for example wetting agents, adhesion-promoting agents, emulsifiers and/or dispersing agents.

Suitable liquid carriers are, for example, water, aliphatic and aromatic hydrocarbons, for example benzene, toluene and xylene, cyclohexanone, isophorone, dimethyl sulphoxide and dimethylformamide, and also mineral oil fractions.

As solid carriers there are suitable, for example, mineral earths, for example Tonsil, silica gel, talc, keolin, attaclay, limestone and silicic acid, and vegetable products, for example meals.

As surface-active agents there may be mentioned, for example, calcium lignin-sulphonate, polyoxyethylenealkylphenol ethers, naphthalenesulphonic acids and salts thereof, phenolsulphonic acids and salts thereof, formaldehyde condensates, fatty alcohol sulphates and also substituted benzenesulphonic acids and salts thereof. The total amount of the active substance(s) in the various preparations may vary within wide limits. For example, the preparations may contain approximately from 10 to 80% by weight of active substance(s), approximately from 90 to 20% by weight of liquid or solid carrier and also, if desired, up to 20% by weight of surface-active agent(s).

The active substances may be applied in the customary manner, for example with water as the carrier in spray liquor quantities of approximately from 100 to 1000 litres per hectare. It is also possible to apply the active substances by the so-called low-volume- or ultra-low-volume-method and it is furthermore possible to apply them in the form of so-called microgranules.

The following components, for example, are used for the manufacture of the preparations: Table I A. Sprayable powder a) 80% by weight of active substance 15% by weight of kaolin 5% by weight of surface-active agents based on the sodium salt of N-methyl-N-oleyl-taurine and the calcium salt of ligninsulphonic acid.

b) 50% by weight of active substance 40% by weight of clay minerals 5% by weight of cellulose pitch 5% by weight of surface-active agents based on a mixutre of the calcium salt of ligninsulphonic acid and alkylphenol-polyglycol ethers.

c) 20% by weight of active substance 70% by weight of clay minerals 5% by weight of cellulose pitch 5% by weight of surface-active agents based on a mixture of the calcium salt of ligninsulphonic acid and alkylphenol-polyglycol ethers.

d) 5% by weight of active substance 80% by weight of Tonsil 10% by weight of cellulose pitch 5% by weight of surface-active agents based on a fatty acid condensation product.

B. Emulsion concentrate 20% by weight of active substance 40% by weight of xylene 35% by weight of dimethyl sulphoxide 5% by weight of a mixture of nonylpheny!-polyoxyethylene and calcium dodecyl-benzene sulphonate.

C. Paste 45% by weight of active substance 5% by weight of sodium aluminium silicate 15% by weight of cetyl-polyglycol ether with 8 moles of ethylene oxide 2% by wieght of spindel oil 10% by weight of polyethylene glycol 23 parts of water.

The novel compounds of the present invention may be manufactured, for example, by the process of the present invention, as defined below.

The present invention accordingly further provides a process for the manufacture of the compounds of the general formula I, wherein a compound of the general formula II

in which R17 has the meaning given above, is A) hydroxylated in the presence of osmium tetroxide as catalyst with tert.-butyl hydroperoxide or N-methylmorpholine N-oxide to form a compound of the general formula III

in which R17 has the meaning given above, or B) treated with silver acetate and iodine in aqueous acetic acid to form a compound of the general formula IV

in which R17 has the meaning given above, and the resulting compound is oxidised with a per-acid, any double bond in the C22-C23-position being protected by bromination during the oxidation, and, if desired, before and/or after the oxidation, any 2- and/or 3-hydroxyl group(s) is/are converted into (an) acyloxy group(s) and/or any 2- and/or 3-acyloxy group(s) is/are converted into (a) hydroxyl group(s), and, if desired, any resulting compound of the general formula I, in which R2 and R3 each represents a hydrogen atom, is converted into a compound of the general formula I in which R2 and R3 together represent a group of the formula

X and Y having meanings given above.

in order to produce the compounds of the general formula I, sterins, for example cholesterin, stigmasterin, brassicasterin or p-sitosterin, may be used as starting materials and reacted in a manner known perse to form the A2-6-keto-steroids of the general formula II. [In Heir. 49, 1581(1966)].

The further reaction to form 2a,3a-cis-glycols or 2P,3P-cis-glycols of the general formula Ill may be carried out in accordance with known methods, namely by osmium tetroxide-catalysed hydroxylation with 80% tert-butyl hydroperoxide [K.B. Sharpless JACS 98, 1986 (1976)] or with Nmethyl-morpholine N-oxide (V. van Rheen, Tetrahedron Lett. 1976, 1973).

The 2P,3P-cis-glycols or derivatives thereof of the general formula IV may be obtained by the Provost reaction with silver acetate and iodine in aqueous acetic acid [In Helv. 49. 1581 (1966)].

The B-ring lactone part of the compounds of the general formula I is produced by the Baeyer Villiger oxidation with peracids, for example trifluoroperacetic acid, performic acid or permaleic acid, of the 6-keto-steroids of the general formulae III and IV. In the case of compounds having a C22-C23 double bond in the side chain, this double bond must be protected by bromination before the lactonisation.

After the Baeyer-Villiger oxidation the C22-C23 double bond can be regenerated with zinc in acetic acid.

The optional conversion of a compound of the general formula I containing free hydroxyl groups in the 2- and 3-positions into a compound of the general formula I in which R2 and R3 together represent a group of the formula

may be carried out, for example, by reacting it with a) boron trifluoride etherate, if desired dissolved in an organic solvent, b) orthoacetic acid triethyl ester, if desired in the presence of a catalyst, dissolved in an organic solvent, c) acetophenone in perchloric acid, or d) diethyl carbonate and a catalytic amount of sodium methoxide.

The following Examples illustrate the invention. These Examples illustrate the manufacture of the compounds of the present invention.

Example 1 a) 3.56 g of 24S-ethyl-5a-cholesta-2,22-dien-6-one were dissolved in 60 ml of tert.-butanol, 4 ml of a 20% tetraethylammonium hydroxide solution were added, the whole was cooled to 0 C and 12 ml of 80% tert.-butyl hydroperoxide and 6 ml of an osmium tetroxide solution (prepared from 250 mg of OsO4, 49.75 ml of tert.-butanol and 0.25 ml of 80% tert.-butyl hydroperoxide) were added. The reaction solution was stirred for 6 hours at room temperature, poured into a 5% sodium hydrogen sulphite solution and extracted with ethyl acetate. The extract was washed with water, dried over soduim sulphate and concentrated by evaporation. After recrystallisation from methylene chloride/methanol, 2.3 g of 2a,3a-dihydroxy-24S-ethyl-5a-cholest-22-en-6-one were obtained.

M.p.: 234.5-235.50C.

b) 2.2 g of 2a,3a-dihydrnxy-24S-ethyl-5or-cholest-22-en-6-one were dissolved in 15 ml of pyridine, 8 ml of acetic anhydride and 220 mg of 4-dimethylaminopyridine were added and the whole was left to stand for 17 hours at 20"C. The whole was then precipitated in ice-water and the product, the crude diacetate, was suction-filtered, washed and dried.

c) 0.28 ml of bromine was added to 2.6 g of the crude diacetate in 30 ml of ether and 30 ml of glacial acetic acid and the whole was then stirred for 10 minutes at room temperature. For working up, the whole was diluted with ether, washed until neutral with water and concentrated by evaporation in vacuo. 3.2 g of crude 2a-3a-diacetoxy-22,23-dibrnmo-24-ethyl-5a-cholestan-6-one were thus obtained.

d) 4.5 ml of 30% hydrogen peroxide were suspended in 28 ml of methylene chloride, the suspension was cooled to -1 00C and 27.7 ml of trifluoroacetic anhydride were slowly added dropwise so that the internal temperature did not exceed +1 00C. 3.2 g of 2a,3a-diacetoxy-22,23-dibrnmo-24- ethyl-5-cholestan-6-one, dissolved in 25 ml of methylene chloride, were then added and the whole was stirred for 40 minutes at room temperature. The whole was then diluted with methylene chloride and washed in succession with water, a 5% sodium carbonate solution and with water, dried and concentrated in vacua. The residue was heated in 100 ml of acetic acid with 5 g of zinc dust for 1 hour on a steam bath.The zinc was filtered off and the filtrate was diluted with methylene chloride, washed until neutral with water and concentrated by evaporation. After chromatography over silica gel (gradient elution toluene/ethyl acetate) and crystallisation from acetone/hexane, 1.5 g of 2a,3a- diacetoxy-24-ethyl-7-oxa-B-homo-5a-cholest-22-en-6-one, m.p. 221-2230C, and 310 mg of 2a,3a-diacetoxy-24-ethyl-6-oxa-B-homo-5a-cholest-22-en-7-one, m.p. 202--204 C, were obtained.

Example 2 a) 3.2 g of silver acetate and 1.9 g of iodine were added to a solution of 2 g of 24-ethyl-5cholesta-2,22-dien-6-one in 270 ml of glacial acetic acid and 3.7 ml of water and the whole was heated, while stirring, for 3 hours at 450 C. After filtering off the silver salts and washing with chloroform, the filtrate was diluted with chloroform, washed with water, sodium thiosulphate and water, dried and concentrated. After crystallisation from acetone/hexane, 1.2 g of 2P-acetoxy-3P- hydroxy-24-ethyl-5-cholest-22-en-6-one were obtained.

M.p. 192-1940C.

b) After bromination of the A22-double bond, Baeyer-Villiger oxidation and zinc reduction, as described in Example 1 c) and 1 d), the crude product was chromatographed over silica gel. By gradient solution with chloroform/acetone, there was obtained, after recrystallisation from hexane/ether, a 75% yield of 2ss-acetoxy-3ss-hydroxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one, m.p. 1 51-1 53 0C, and a 1 0% yield of 2ss-acetoxy-3ss-hydroxy-24-ethyl-6-oxa-B-homo-5α-cholest-22-en-7-one, m.p.

175-1760C.

Example 3 a) A solution of 500 mg of potassium hydroxide in 10 ml of methanol was added to 2.2 g of 2P- acetoxy-3-hydrnxy-24-ethyI-7-oxa-B-homo-5a-cholest-22-en-6-one in 50 ml of methanol and the whole was stirred for 30 minutes at room temperature. The whole was acidified with acetic acid and precipitated in ice-water, and the product was suction-filtered, washed and dried. After crystallisation from chloroform/ether, 1.7 g of 2,3-dihydroxy-2 4-ethyl-7-oxa-B-homo-5a-cholest-22-en-6-one, m.p. 21 30C, were obtained.

b) 500 mg of 2,3-dihydrnxy-24-ethyI-7-oxa-B-homo-5a-choIest-22-en-6-one in 4 ml of pyridine were cooled to -1 00C, 0.5 ml of acetic anhydride was added and the whole was stirred for 3.5 hours at -5 to 0 C. After precipitation in ice-water, the product was suction-filtered, washed and dried, and then recrystallised from acetone/hexane. 410 mg of 3ss-acetoxy-2ss-hydroxy-24-ethyl-7-oxa- B-homo-5a-cholest-22-en-6-one, m.p. 1 82-1 840 C, were obtained.

Example 4 1 g of 2rx,3rx-dihydroxy-7-oxa-B-homo-5rx-cholestan-6-one was dissolved in 10 ml of pyridine, the solution was cooled to 0 C and 1 ml of acetic anhydride was added. The whole was stirred for 5 hours at 0--5 0 C, then poured into ice-water, and the product was suction-filtered, washed and dried.

After recrystallisation from pentane, 950 mg of 2a-acetoxy-3a-hydrnxy-7-oxa-B-homo-5a-cholestan- 6-one, m.p. 165.5--167"C, were obtained.

Manufacture of the starting material a) 25 g of 5a-cholest-2-en-6-one were dissolved in 140 ml of tetrahydrofuran, and 1 4 g of Nmethyl-morpholine N-oxide, 25 ml of water and 50 ml of tert.-butanol were added, and then, while stirring, a solution of 250 mg of asmium tetroxide in 50 ml of tetrahydrofuran was added. The reaction solution was stirred for 1 7 hours at room temperature with the exclusion of light. The reaction solution was then precipitated in 7 litres of ice-water to which had been added 50 ml of 2N sulphuric acid and 1 g of sodium sulphide, the product was suction-filtered, washed with water and dissolved in chloroform, and the resulting solution was concentrated by evaporation in vacuo.The crude product (30 g) was dissolved in 140 ml of pyridine and, after the addition of 70 ml of acetic anhydride and 3 g of 4dimethylaminopyridine, the whole was left to stand for 1 6 hours at room temperature. After precipitation in water, suction-filtration of the product, washing with water and drying, chromatography over silica gel was carried out. After recrystallisation from ethanol, a 75% yield of 2a,3a-diacetoxy-5cr-cholestan-6-one, m.p. 1 50.0-1 51 .50C, and a 1 5% yield of 2ss,3ss-diacetoxy-5- cholestan-6-one, m.p. 1 83.5-1 850C, were obtained.

b) 26 ml of 30% hydrogen peroxide were suspended in methylene chloride, the suspension was cooled to -1 00C and 161 ml of trifluoroacetic an hydroxide were slowly added dropwise so that the internal temperature did not exceed +1 00C. 27.2 g of 2a,3a-diacetoxy-5-choIestan-6-one, dissolved in 160 ml of methylene chloride, were then added and the whole was stirred for 40 minutes at room temperature. For working up, the whole was diluted with methylene chloride and washed in succession with water, a 5% sodium carbonate solution and with water and concentrated in vacua.After chromatography over silica gel and recrystallisation from acetone/hexane, an 81% yield of 2a,3a- diacetoxy-7-oxa-B-homo-5a-cholestan-6-one, m.p. 183-1 840 C, and a 6.2% yield of 2a,3a- diacetoxy-6-oxa-B-homo-5a-cholestan-7-one, m.p. 245--247 C, were obtained.

c) 28.3 g of 2a,3a-diacetoxy-7-oxa-B-homo-Sa-cholestan-6-one were dissolved in 500 ml of methanol and, after the addition of a solution of 14 g of potassium hydroxide in 1 50 ml of methanol, the whole was stirred for 30 minutes at room temperature. The whole was then acidified with acetic acid and precipitated in ice-water, and the product was suction-filtered, washed with water and dried.

After recrystallisation from acetone/pentane, 22.4 g (a 95% yield) of 2a,3a-dihydroxy-7-oxa-B-homo5a-cholestan-6-one, m.p. 138--140 C, were obtained.

Example 5 a) 1.1 g of 2a,3a-diacetoxy-6-oxa-B-homo-Sa-cholestan-7-one were hydrolysed as described in Example 4c). 785 mg of 2a,3a-dihydrnxy-6-oxa-B-homo-5a-cholestan-7-one of m.p. 21 6.5-21 80C were thus obtained.

b) 250 mg of 2a,3a-dihydrnxy-6-oxa-B-homo-5a-cholestan-7-one were dissolved in 2 ml of pyridine, the solution was cooled to -1 00C, 0.24 ml of acetic anhydride was added and the whole was stirred for 4 hours at -5 to OOC. After precipitation in ice-water, suction-filtration of the product, washing and drying, recrystallisation from acetone/hexane was carried out. 210 mg of 2a-acetoxy-3ar- hydroxy-6-oxa-B-homo-5-cholestan-7-one, m.p. 1 99-201 C, were obtained.

Example 6 600 mg of 2a,3a-dihydroxy-24-methyl-6-oxa-B-homo-5a-cholest-22-en-7-one were acetylated as described in Example 5b). 515 mg of 2-acetoxy-3a-hydroxy-24-methyI-6-oxa-B-homo-5a- cholest-22-en-7-one, m.p. 1 73-1 740 C, were obtained.

Manufacture of the starting material 24-Methyl-5a-cholesta-2,22-dien-6-one was prepared from brassicasterin according to a known process and this compound was reacted as described in Example 1 and then hydrolysed as described in Example 4c).

Example 7 1 g of 2P,3P-dihydroxy-7-oxa-B-homo-5a-cholesta n-6-one was dissolved in 100 ml of acetone and 100 ml of tetrahydrofuran, the solution was cooled to OOC, 0.5 ml of boron trifluoride etherate was added and the whole was stirred for 30 minutes at O to 50C. After the addition of 1 ml of pyridine, the whole was concentrated in vacuo and the residue was recrystallised from methylene chloride/isopropyl ether. 731 mg of 2ss,3ss-isopropylidenedioxy-7-oxa-B-homo-5a-cholestan-6-one, m.p. 216-21 70C, were obtained.

The following were manufactured in an analogous manner 2a,3a-isoprnpylidenedioxy-7-oxa-B-homo-Sa-cholestan-6-one, m.p.216217 C, and 2α,3α-isopropylidenedioxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one, m.p. 1 57- 1580C.

Example 8 900 mg of 2α,3α-dihydroxy-7-oxa-B-homo-5α-choíestan-6-one were dissolved in 10 ml of pyridine, the solution was cooled to OOC, 1.8 ml of valeric anhydride were added and the whole was stirred for 10 hours at 0 to 50C. After working up as described in Example 4, 950 mg of 2cz-valeryloxy- 3α-hydroxy-7-oxa-B-homo-5α-cholestan-6-one, m.p.92--94 C, were obtained.

Example 9 23a-Diacetoxy-24-ethyI-7-oxa-B-homo-5a-cholest-22-en-6-one was hydrolysed and partially acetylated as described in Example 3. A 70% yield of 2α-acetoxy-3α-hydroxy-24-ethyl-7-oxa-B-homo- 5a-cholest-22-en-6-one, m.p. 1 58-1 600 C, was obtained.

Example 10 900 mg of 2a,3cx-dihydroxy-7-oxa-B-homo-5cr-cholestan-6-one were dissolved in 10 ml of pyridine, the solution was cooled to OOC, 1 ml of ethoxyacetic anhydride was added and the whole was stirred for 5 hours at 0 to 50 C. After working up as described in Example 4 and recrystallisation from acetone/hexane, 720 mg of 2,α-ethoxyacetoxy-3α-hydroxy-7-oxa-B-homo-5-cholestan-6-one, m.p.

1 72-1 730C, were obtained.

Example 11 300 mg of 2α,3α-dihydroxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one were stirred in 3 ml of pyridine with 780 mg of phenylacetic anhydride for 10 hours at 0 to 50C. After working up and recrystallisation from acetone/hexane, 21 0 mg of 2α-phenylacetoxy-3α-hydroxy-24-ethyl-7-oxa-B- homo-5a-cholest-22-en-6-one, m.p. 1 85-1 860C, were obtained.

Example 12 0.75 ml of orthoacetic acid triethyl ester was added to 500 mg of 2cz,3cr-dihydroxy-7-oxa-B- homo-5 a-cholesta n-6-one in 50 ml of benzene, and 5 mg of p-toluenesulphonic acid were added. The solution was stirred for 20 minutes at room temperature, 3 drops of pyridine were added and the whole was concentrated by evaporating in vacuo. The residue was dissolved in methylene chloride, washed with water, dried over sodium sulphate and concentrated by evaporation. 605 mg of 2,3a- (1-ethoxy-ethyZidenedioxy)-7-oxa-B-homo-5a-cholestan-6-one, m.p. 1 50-1 540 C, were thus obtained.

The following were manufactured in an analogous manner 2sx,3-1 -ethoxy-ethylidenedioxy)-6-oxa-B-homo-5a-cholestan-7-one, m.p. 122--124 C, 2α,3α-(1-ethoxy-propylidenedioxy)-7-oxa-B-homo-5α-cholestan-6-one (using orthopropionic acid triethyl ester instead of orthoacetic acid triethyl ester), m.p. 115-11 80C, 2α,3α-methoxy-methylenedioxy)-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one (using orthoformic acid trimethyl ester instead of orthoacetic acid triethyl ester), m.p. 96--98 C, and 2ss,3ss-(1 -ethoxy-ethylidenedioxy)-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one, m.p 1231250C.

Example 13 1.5 ml of acetophenone and 0.1 ml of boron trifluoride etherate were added to 500 mg of 2a,3adihydroxy7-oxa-B-homo-5-cholestan-6-one in 5 ml of tetrahydrofuran and the whole was heated under reflux for 3 hours. The whole was then concentrated in vacuo, 1 ml of pyridine was added and the whole was concentrated by evaporation under a high vacuum. After triturating with hexane, 465 mg of amorphous 2α,3-(1-methyl-1-phenyl-methylenedioxy)-7-oxa-B-homo-5α-cholestan-6-one were obtained as a diastereoisomeric mixture of m.p. 130.5--132 C.

Example 14 500 mg of 2α,3α-dihydrnxy-7-oxa-B-homo-5α-cholestan-6-one were dissolved in 1 5 ml of diethyl carbonate, the solution was heated to the boiling point and, when 2 ml of diethyl carbonate had distilled off, 30 mg of sodium methoxide were added. A few ml were distilled off from the reaction solution in the course of 3 minutes. After cooling, 0.15 ml of glacial acetic acid was added and the whole was concentrated by evaporation in vacuo. The residue was recrystallised from acetone/hexane.

450 mg of 2a,3ct-carbonyidioxy-7-oxa-B-homo-5cr-cholestan-6-one of m.p. 203.5-2050C were thus obtained.

The following were manufactured in an analogous manner 2α,3α-carbonyldioxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one, m.p. 193-1 950C, and 2ss,3ss-carbonyidioxy-7-oxa-B-homo-5a-ch oí estan-6-one, m.p. 212--214 C.

Example 15 300 mg of 2(x,3sx-dihydroxy-7-oxa-B-homo-5c4-cholestan-6-one were dissolved in 2 ml of benzaldehyde, 0.02 ml of 70% perchloric acid was added and the whole was stirred for 2 hours at room temperature. The solution was then neutralised with pyridine, diluted with hexane and chromatographed over silica gel. Using hexane/ethyl acetate (6:4) 258 mg of 2a,3 a-benzylidenedioxy- 7-oxa-B-homo-5a-cholestan-6-one were eluted and were recrystallised from ether/pentane. M.p.: 1 37-1390C.

The following were manufactured in an analogous manner 2a,3a-benzylidenedioxy-6-oxa-B-homo-5a-cholestan-7-one, m.p. 1 79-1 800 C, 2,3-benzyIidenedioxy-6-oxa-B-homo-5a-cholestan-7-one, m.p. 129-131 0C, and 2ss,3ss-benzylidenedioxy-7-oxa-B-homo-5a-cholestan-6-one, m.p. 1 53-1 550C.

The compounds according to the present invention are, in general, crystalline colourless and odourless substances that are sparingly soluble in water, soluble to a certain extent in aliphatic hydrocarbons, for example petroleum ether, hexane, pentane and cyclohexane, and readily soluble in halogenated hydrocarbons, for example chloroform, methylene chloride and carbon tetrachloride, aromatic hydrocarbons, for example benzene, toluene and xylene, ethers, for example diethyl ether, tetrahydrofuran and dioxan, carboxylic acid nitriles, for example acetonitrile, ketones, for example acetone, alcohols, for example methanol and ethanol, carboxylic acid amides, for example dimethylformamide, and sulphoxides, for example dimethyl sulphoxide.

The following Examples also illustrate the invention. These Examples illustrate the possible applications for the compounds of the present invention, in the form of preparations as indicated above.

Example 16 Promotion of growth in French beans In a series of tests French beans of the variety "Pinto" were cultivated in a climatic chamber at 250C and 90% atmospheric humidity under the effect of light having a high proportion of intensity in the region of 660 nm and a very low proportion in the region of 730 nm.

After 6 days' cultivation, 10 and 50 y9, respectively, of the compounds to be tested listed in the Table below were dissolved in solvents and applied to the developing second internodium.

3 Days after the application, the extension of the internodia was measured and the percentage increase in length in comparision with a control was determined.

The results of this series of tests are given in the following Table.

Percentage Promotion Compounds of the invention lOg 50 5Og 2a-Acetoxy-3 ct-hydroxy-B-homo-7- oxa-5a-cholestan-6-one 292 125 2a,3a-Carbonyldioxy-B-homo-7 oxa-5a-cholestan-6-one 190 304 2 Acetoxy-3 a-hyd roxy-B-homo-6- oxa-5a-cholestan-7-one 162 125 2ar,3a-(1 -Ethoxy-ethylidenedioxy) B-homo-7-oxa-5a-cholestan-6-one 165 1 62 2,3a-(1 1 -Methyl-l -phenyl-methyl enedioxy)-B-homo-7-oxa-5a cholestan-6-one 152 342 Agents for comparison 2a,3sz,22S,23S-Tetrahydroxy-24- ethyl-B-homo-7-oxa-5a-cholestan- 89 6-one 89 114 4-(3-lndolyl)-butyric acid 51 38 Control 100 100 The results show that, under the stated test conditions, the compounds according to the present invention brought about a more intense extension than did the agents used for comparison and the control.

In contrast, the agents used for comparison brought about only a more or less marked promotion of the growth in thickness which, in some cases, even led to a compression of the internodia.

Example 17 Stimulation of root growth in Mung beans In a series of tests mung beans were germinated under greenhouse conditions in aqueous emulsions of the compounds to be tested listed in the Table below in a concentration of 0.01% by weight.

After 6 days, the length of the roots of the germinated plants was determined.

The following Table shows the results of this series of tests in the form of percentages.

Percentage Compounds of the invention stimulation 2α-Acetoxy-3α-hydroxy-B-homo-7- oxa-5c-cholestan-6-one 180 2a3 a.Carbonyldioxy-B-homo-7 -oxa- 5α-cholestan-6-one 160 2cz-Acetoxy-3 cr-hydroxy-B-homo-6- oxa-5 a-cholestan-7-one 160 2 a,3 sz-(1 -Ethoxy-ethylidenedioxy) B-homo-7-oxa-5a-choíestan-6-one 200 2a,3a-(1 -Methyí-1 -phenyl-methylene dioxy)-B-homo-7-oxa-5α;-cholestan- 6-one 150 Agent for comparison Gibberellic acid (GA > ) 80 Control 100 Example 18 Increasing the resistance of crop plants In a series of tests the crop plants listed in the Table below were treated by a pre-emergence procedure with aqueous emulsions of the compounds I and II to be tested or mixtures thereof in the doses indicated.One week after the treatment, the results thereof were assessed on a scale extending from 0 to 10, 0 representing 100% destruction and 10 representing no damage.

Components Doseinkg/ha Tomato Cucumber Wheat Soya Maize Beet 2a-Acetoxy-3 a hydroxy-B-homo 7 -oxa-Sa-cholestan 6-one 1 0.02 10 10 10 10 10 10 4-Chloro-5-methyl amino-2Aa,a,a trifluoro-m-tolyl) pyridazin-3-one (Norflurazon) II 0.3 4 3 5 9 3 5 3.0 1 1 1 4 2 1 1+11 0.3+0.02 8 7 10 10 9 7 1+11 3.0+0.02 6 5 8 10 7 7 Control - 10 10 10 10 10 10

It can be seen that the compound according to the present invention increases the resistance of the plants to the known herbicide.

Claims

1. A brassinosteroid derivative of the general formula I

in which R17 represents a C8-C10-alkyl group or a C8-C10-alkenyl group, Z represents a group of the formula

2. A compound as claimed in claim 1, wherein R17 represents a 2-methyl-heptan-6-yl, 2-methyl-3-ethyl-hept-4-en-6-yl, 2,3-dimethyl-hept-4- en-6-yl, 2-methyl-3-ethyl-heptan-6-yl or 2,3-dimethyl-heptan-6-yl group, Z represents a group of the formula

and R2 and R3 each represents a hydrogen atom, a formyl group, a C2-C7-alkyl-CO- group, a C2-C7-alkoxy-C1-C3-akyl-CO- group, an aryl-CO-- group or an aryl-C1-C2-alkyl-CO- group, or together represent a group of the formula

3. 2a,3a-Diacetoxy-24-ethyl-7-oxa-B-homo-5a-cholest-22-en-6-one.

4.2α,3α-Diacetoxy-24-ethyl-6-oxa-B-homo-5a-cholest-22-en-7-one.

5.2ss-Acetoxy-3ss-hydroxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one.

6.2ss-Acetoxy-3ss-hydroxy-24-ethyl-6-oxa-B-homo-5α-cholest-22-en-7-one.

7.3iB-Acetoxy-2A-hydroxy-24-ethyl-7-oxa-B-homo-5-cholest-22-en-6-one.

8. 2a-Acetoxy-3 a-hydroxy-7-oxa-B-homo-5 a-cholestan-6-one.

9. 2a-Acetoxy-3a-hydroxy-6-oxa-B-homo-5a-cholestan-7-one.

10.2α-Acetoxy-3α-hydroxy-24-methyl-6-oxa-B-homo-5α-cholest-22-en-7-one.

11.2A,3p-lsopropylidenedioxy-7-oxa-B-homo-5a-cholestan-6-one.

12. 2a,3a-lsopropylidenedioxy-7-oxa-B-homo-5a-cholestan-6-one.

13.2α,3α-Isopropylidenedioxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one.

14. cr-Valeryloxy-3ce-hydroxy-7-oxa-B-homo-5cr-cholesta n-6-one.

15.2α-Acetoxy-3α-hydroxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one.

1 6. 2a-Ethoxyacetoxy-3 cr-hydroxy-7-oxa-B-homo-5-cholestan-6-one.

17.2α-Phenylacetoxy-3α-hydroxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one.

1 8. 2a,3a-( 1 -Ethoxy-ethylidenedioxy)-7-oxa-B-homo-5a-cholestan-6-one.

19.2α,3α-(1-Ethoxy-ethylidenedioxy)-6-oxa-B-homo-5α-cholestan-7-one.

20.2α,3α-(1-Ethoxy-propylidenedioxy)-7-oxa-B-homo-5α-cholestan-6-one.

21. 2a,3a-( 1 -Methoxy-methylenedioxy)-24-ethyl-7-oxa-B-homo-5a-cholest-22-en-6-one.

22.2ss,3ss(1-Ethoxy-ethylidenedioxy)-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one,

23.2α,3α-(1-Methyl-1-phenyl-methylenedioxy)-7-oxa-B-homo-5α-cholestan-6-one.

24.2α,3α-Carbonyldioxy-7-oxa-B-homo-5α-cholestan-6-one.

25.2α,3α-Carbonyldioxy-24-ethyl-7-oxa-B-homo-5α-cholest-22-en-6-one.

26.2p,3,B-Ca rbonyidioxy-7-oxa-B-homo-5α-cholesta n-6-one.

27.2α,3α-Benzylidenedioxy-7-oxa-B-homo-5α-cholestan-6-one.

28.2α,3α-Benzylidenedioxy-6-oxa-B-homo-5α-cholestan-7-one.

29. 2ss,3ss-BenzyIidenedioxy-6-oxa-B-homo-5α-cholestan-7-one.

30.2ss,ss3-Benzylidenedioxy-7-oxa-B-homo-5α-cholestan-6-one.

31.2p,3,8-Di hydroxy-24-ethyl-7-oxa-B-homo-5-cholest-22-en-6-one.

32. 2,a,3a-Diacetoxy-7-oxa-B-homo-5a-cholestan-6-one.

33. 2a,3a-Diacetoxy-6-oxa-B-homo-5a-cholestan-7-one.

34. 2a,3a-Dihydroxy-7-oxa-B-homo-5a-cholestan-6-one.

35.2c2,3cz-Dihydroxy-6-oxa-B-homo-5cx-cholestan-7-one.

36. A process for the manufacture of a compound of the general formula I given in claim 1, in which R,7, Z, R2 and R3 have the meanings given in claim 1, wherein a compound of the general formula il

in which R,7 has the meaning given above, is A) hydroxylated in the presence of osmium tetroxide as catalyst with tert.-butyl hydroperoxide or N-methylmorpholine N-oxide to form a compound of the general formula III

in which R17 has the meaning given above, and the resulting compound is oxidised with a peracid, any double bond in the C22-C23-position being protected by bromination during the oxidation, and, if desired, before and/or after the oxidation, any 2- and/or 3-hydroxyl group(s) is/are converted into (an) acyloxy group(s) and/or any 2- and/or 3-acyloxy group(s) is/are converted into (a) hydroxyl group(s), and, if desired, any resulting compound of the general formula I, in which R2 and R3 each represents a hydrogen atom, is converted into a compound of the general formula I in which R2 and Ra together represent a group of the formula

X and Y having meanings given in claim 1.

37. A process as claimed in claim 36, conducted substantially as described herein.

38. A process for the manufacture of a compound as claimed in claim 1, conducted substantially as described in any one of Examples 1 to 1 5 herein.

39. A preparation for regulating the growth of plants, which comprises at least one compound of the general formula I given in claim 1, in which R17,Z, R2 and R3 have the meanings given in claim 1, in admixture with an auxiliary.

40. A preparation as claimed in claim 39, wherein the compound of the general formula I is a compound as claimed in claim 2.

41. A preparation as claimed in claim 39, wherein the compound of the general formula I is the compound claimed in any one of claims 3 to 35.

42. A preparation for regulating the growth of plants, which comprises at least one compound of the general formula I given in claim 1, in which R , Z, R2 and R3 have the meanings given in claim 1, in admixture or conjunction with a suitable carrier.

43. A preparation as claimed in claim 42, wherein the compound of the general formula I is a compound as claimed in claim 2.

44. A preparation as claimed in claim 42, wherein the compound of the general formula I is the compound claimed in any one of claims 3 to 35.

45. A preparation as claimed in any one of claims 42 to 44, which is in the form of a powder, a strewable preparation, granules, a solution, an emulsion or a suspension.

46. A preparation as claimed in any one of claims 42 to 45, which also contains one or more active substances selected from defoliants, plant-protecting agents, pesticides and herbicides other than compounds of the general formula I.

47. A preparation as claimed in any one of claims 42 to 46, wherein the total amount present of active substance or substances is approximately 10 to 80% by weight.

48. A preparation as claimed in any one of claims 42 to 47, which also contains one or more surface-active agents in a total amount of up to 20% by weight.

49. Any one of the preparations as claimed in claim 42 and substantially as described in Table I herein.

50. Any one of the preparations as claimed in claim 42 and substantially as described in Example 1 7 herein.

51. A method of regulating the growth of a living plant, wherein the living plant and/or the area in the vicinity of the living plant is/are treated with a compound of the general formula I given in claim 1, in which R17,Z, R2 and R3 have the meanings given in claim 1.

52. A method as claimed in claim 51, wherein the treatment is carried out with a compound as claimed in claim 2.

53. A method as claimed in claim 51, wherein the treatment is carried out with the compound claimed in any one of claims 3 to 35.

54. A method as claimed in claim 51, wherein the treatment is carried out with a preparation as claimed in any one of claims 42 to 50.

55. A method as claimed in any one of claims 51 to 54, wherein a single compound of the general formula I is used for the treatment in an amount within the range of from 0.001 to 1 kg per hectare.

56. A method as claimed in any one of claims 51 to 54, wherein two or more compounds of the general formula i are used for the treatment in a total amount within the range of from 0.001 to 1 kg per hectare.

57. A method as claimed in any one of claims 51 to 56, wherein the plant is a leguminous plant.

58. A method as claimed in claim 57, wherein the leguminous plant is a soya bean plant.

59. A method as claimed in claim 51, conducted substantially as described in any one of Examples 16 to 18 herein.

60. A method of regulating the growth of plants in an area of land, wherein the area is treated with a compound of the general formula I given in claim 1, in which Err7, Z, R2 and R3 have the meanings given in claim 1.

61. A method as claimed in claim 60, wherein the treatment is carried out with a compound as claimed in claim 2.

62. A method as claimed in claim 60, wherein the treatment is carried out with the compound claimed in any one of claims 3 to 35.

63. A method as claimed in claim 60, wherein the treatment is carried out with a preparation as claimed in any one of claims 42 to 50.

64. A method as claimed in any one of claims 60 to 63, wherein a single compound of the general formula I is used for the treatment in an amount within the range of from 0.001 to 1 kg per hectare.

65. A method as claimed in any one of claims 60 to 63, wherein two or more compounds of the general formula I are used for the treatment in a total amount within the range of from 0.001 to 1 kg per hectare.

66. A method as claimed in any one of claims 60 to 65, wherein the area of land is a crop area.

67. A method as claimed in claim 66, wherein the crop is a leguminous crop.

68. A method as claimed in claim 67, wherein the leguminous crop is a soya bean crop.

69. A method of dressing seeds, wherein the seeds are treated with a compound of the general formula I given in claim 1, in which R17, Z, R2 and R3 have the meanings given in claim 1.

70. A method as claimed in claim 69, wherein the treatment is carried out with a compound as claimed in claim 2.

71. A method as claimed in claim 69, wherein the treatment is carried out with the compound claimed in any one of claims 3 to 35.

72. A method as claimed in claim 69, wherein the treatment is carried out with a preparation as claimed in any one of claims 42 to 50.

73. A pack which comprises at least one compound of the general formula I givne in claim 1, in which R17, Z, R2 and Ra have the meanings given in claim 1, together with instructions for its use in regulating the growth of living plants.

74. A pack as claimed in claim 73, wherein the compound of the general formula I is a compound as claimed in claim 2.

75. A pack as claimed in claim 73, wherein the compound of the general formula I is the compound claimed in any one of claims 3 to 35.