CA1161657A - N-substituted alanine herbicidal composition - Google Patents

Abstract

A B S T R A C T
Herbicidally active compositions comprising a compound of formula I

Description

This invention relates ~o a he-rbicidally-active composition comprising certain N-substituted alanine compounds.
~he her~icidal composition according to the invention comprises a carrier and/or a surface-active agent and as active ingredient at least one N-substituted alanine compound having the general formula:

X _ ~ _ NH-CH-COR ~I) Y
wherein X is a fluorine or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z i.s a hydrogen atom or an alkoxy 1~ group; and R is a group of formula -ORl J
in which Rl 1S hydrogen, a metal salt-forming or an optionally alkyl substituted ammonium ion, an optionally substituted alkyl, cycloalkyl, aryl, alkenyl or alkaryl group; or a group of formula -SR2 in which R2 is an optionally substituted alkyl, cycloalkyl, aryl, alkenyl or alkaryl group, with the proviso that if Z is hydrogen, and both X and Y are chlorine, then Rl is other . than hydrogen.

- 2 -

- 3 ~6~6~7 A preferred herbicidal composition according to the invention is one in which the active in~,redient is an N-substituted alanine compound with the general formula (II).

X ~/ ~ N~-~H-COOR (Il) ~ CH3 y where X is fluorine or chlorine, Y is chlorine; ~ is a 5 hydrogen atom or an alkyl group of 1 to l~ carbon atoms for example a methyl,ethyl or isopropyl group.
It will be appreeiated that the N-substituted eompounds aeeording to the invention can exhibit optical isomerism. The indiv:Ldual isomers together with mixtures thereof are included within the scope of the inventlon.
The Applieant has observed that in the majority of cases one of the optically active isomers (the dextro-rotatcry isomer) of the N-substituted alanine compounds is more herbicidally active than the other isomer~ ~ccordingly a particularly preferred herbicidal composition according to the invention is one in which the N-substituted alanine compound, as defined in formula (I), is present in the dextro-rotatory form.
The eomposition according to the invention exhibits good herbicidal activity against broad-leaved weeds when applied as a foliar spray. In particular it gives improved selective control of these weeds in cereal crops, especiaIly in barley crops. The invention therefore also relates to a method of eradicating or controllin~

broad-leaved weeds which comprises applying to the weeds or their habitat a herbicidally effective amount of the N-substituted alanine compound of general formula (I), wherein X is a fluorinc or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z is a hydrogen atom or an alkoxy group; and R is a group of formula -~Rl in which Rl is hydrogen, a metal salt-forming or an optionally alkyl substituted ammonium ion, an optionally substituted alkyl, cycloalkyl, aryl, alkenyl or alkaryl group; or a group of formula -SR2 in which R2 is an optionally substituted alkyl, cycloalkyl, aryl, alkenyl or alkaryl group.
Preferably, a herbicidally effective amount of a compound of general formula ~II) is used.
Some of the compounds of formula (I) are novel compounds and they are believed to be the following: N-(3,4-dichlorophenyl)alanine, isopropyl ester and methyl 2-(3-chloro-4-fluorophenyl)amino-3-methoxy propionate. The N-substituted alanine compounds may be prepared by conventional methods available to the organic chemist~ e.g. by reaction of an aniline derivative of formula:

X ~3 NH2 y wherein X and Y are as defined above, with a propionic acid derivative of formula:
CH2- ICH-C(:)OH
Z Cl wherein Z is a hydrogen atom or methoxy group, in the presence of a suitable base to absorb the hydrogen halide which is eliminated, for example, sodium bicarbonate. The carboxylic acid product may then be esterified to give the required ester.

~,j L6~

The Applicant has also found that the spectrum of activity of the composition according to the invention may be remarkably increased by including in the composition a second active ingredient, namely a compound from the group of wild oat herbicides having the N"N-disubstituted alanine skructure. Surprisingly although the N-substituted alanine compounds of formula (I) have no activity against grass-like weeds ~including wild oats) the combination gives rise to an increased activity with regard to wild oat, whilst lea~ing the broad-leàved activity unaffected.
Accordingly the present invention further provides a composition for the control of broad-leaved weeds and wild oats comprisine as active ingredients (a) an N-substituted alanine compound having the general formula (I), and (b) an N,N-disubstituted alanine compound of the following general formula:

CQ ~

X ~ N (III) ~ \
~ CH-COR

wherein Y is hydrogen, ~luorine or chlorine; X is chlorine or fluorine; Q is oxygen or sulphur; and R is a group of formula -OR1, in which R1 is hydrogen, a metal salt-forming or an optionally alkyl substituted ammonium ion, an optionally substltuted alkyl, cyclo-a~yl, aryl, alkenyl or alkaryl group;

a group of formula -SR2 in which R~2 ls an optionally substituted alkyl3 cycloalkyl9 aryl,alkenyl or alkaryl group; or a group of formula -NR3R4-or -oN=CR3R4 in which R3 and R each individually is hydrogen, hydroxy, an optionally~substituted alkyl, alkenyl, aryl, alkaryl, heterocyclyl, alkoxy, alkylthio or amino groupg or R3 and R4 togekher represent a polymethylene group optionally interrupted by one or more hetero atoms.
Examples of these N,N-disubstltuted alanine compounds and their methods of synthesis can be found in the following German patent specifications:
OLS 1 643 527, OLS 2 109 910, OLS 2 302,029, 0LS 2 349 970, OLS 2 504 3199 OLS 2 460 691.
Especially preferred N,N-disubstituted alanine compounds are those having the following general formula:
` ~ ~ CQ ~
X ~ N / (IV3 Y \
y C~-COO~, wherein X and Y each individually represent chlorine or `
fluorine and R is a hydrogen atom or an alkyl group containing up to 6 carbon atoms, e.g. methyl, ethyl or isopropyl. Of these compounds the wild oat herbicide especially suitable ~or use in barley crops is the compound having the formula(IV) above wherein:

X= fluorine, Y= chlorine; and ~= iso~ropyl.
The best compounds for use in wheat crops have the formula (IV) above wherein: X = chlorine or fluorine;
Y = chlorine; and R - methyl or ethyl.
As in the case of the N-substituted alanine compounds~, the N,N-disubstituted compounds can also exist in optically active forms and, generally speaking, the laevo-rotator~ isomer is the most active form. Thus, where it is appropriate the N3N-disubstituted alanine compound may be employed in its most active optically-active form in the composition according to the invention.
A particularly preferred herbicidal composition for the control of broad-leaved weeds and w1ld oat is one in which the N-substituted alanine compound as defined in formula (I) is present in the dextro-rotatory form and the N,N-disubstituted alanine compound as defined in formula (III) is present in the laevo-rotatory form.
The invention also includes a method of eradicating or controlling both broad-leaved and ~rass weeds infesting cereal crops at a locus which compr1ses applying to the locus a herbicidally effective amount of an N-substituted alanine compound of formula (I) and an N,N-disubstituted alanine compound of formula (III).
The optional substituents in the alanine derivatives of general formulae(I) and (III) referred to above are preferably one or two chlorine, fluorine, alkyl (1-4C)~

-- 8 ~

or alkoxy (1-4C) groups. The alkyl, alkenyl, alkoxy, alkylthio groups referred to in the above general formulae suitably contain up to ~ carbon atoms, preferably up to 4 carbon atoms. l'he aryl, alkaryl, cycloalkyl~ heterocyclyl and poIymethylene groups suitably contain up to 10 carbon atoms, preferably up to 7 carbon atoms. The hetero-atoms which may be in the polymethylene group or in the heterocyclyl groups can be oxygen, nitrogen or sulphur atoms but are preferably one or two oxygen and/or nitrogen atoms For many years the broad-leaved weeds which infest cereal crops have been successfully controlled by ~iar application of plant gro.wth regulator herbicides such as the phenoxy-alkanoic acid derivatives, known as hormone weed-killers. In an attempt to eradicate both broad-leaved and grass weeds by a single post-emergence application to a cereal crop, it has been observed that the presence of the hormone weedkiller has an antagonistic effect on the activity of N,N-di-substituted alanine wild oat herbicides and the latter's effectiveness is reduced~ leading to a poorer control of the wlld oats than is obtalned by applying to the two types of herbicide separately. Thus the composition according to the invention comprising both types of alanine derivatives has a two-fold advantage over any existing systems for dealing with weed-infested cereal _ 9 ~

crops, namely the ability to control broad-leaved weeds and wild oats in one application to cereal crops and the synergistic effect of the mixture with regard to the selective control of wild oats in cereal crops.
The herbicidal composition according to the invention may be formulated in such a way as to ~acilitate its application to the area to be tested and, conveniently, the composition includes a carrier or a surfactant and usually a carrier and a surfactant.
The term "carrier~' as used herein means a material, which may be inorganic or organic and of synthetic or natural origin, with which the active compound or compounds is mixed or formulated to facilitate its application to the plant, seed, soil or other object to be treatec, or its storage, transport or handling. The carrier may be a solid or a fluid. AnD Of the material usually applied in formulating pesticides may be used as a carrier.
Examples of suitable solid carrier are silicates, clays, for example, kaolinite clay~ synthetic hydrated silicon oxides, synthetic calcium silicates, elements such as for example, carbon and sulphur, natural and synthetic resins such as for example, coumarone resins, rosin, copal, shellac, dammar, polyvinyl chloride and styrene polymers and copolymers, solid polychlorophenols, - 1 o ~ 637 bitumen, asphaltite, ~axes such as for example~ beeswax, paraffirl wax, montan wax and chlorinated mineral waxes, and solid fertilisers, for example superphosphates.
Examples of suitable fluid carriers are water, alcohols, such as for example, isopropanol, ketones such as for example, acetone methyl ethy] keto~, methyl isobutyl ketoreand'cyclohexanone, ethers, aromatic hydro-carbons such as for example, benzene and toluene~
petroleum fractions such as for example, kerosine~ chlorinated hydrocarbons, such as for example, carbon tetrachloride, including liquefied normally vaporous gaseous compounds.
Mixtures of different liquids are often suitable.
The surface-active agent may be a wetting agent, an emulsifying agent or a dispersing agent; it may be non-ionic or ionic. Any of the surface-active agents usually applied in formulating herbicides may be used.
Examples of suitable surface-active agents are the sodium or calcium salts of polyacrylic acids, the condensation products of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/~r propylene oxide; partial esters of the above fatty acids with glycerol, sorbitan3 sucrose or pentaerythritol; condensation products of alkyl phenols, for example p-octylphenol or p-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; and alkali metal salts, preferably sodium salts, of sulphuric 6~7 acid esters or sulphinic acids containing at least 10 carbon atoms in the molecule, for example3 sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sul~honated castor oil~ and sodium alkylaryl sulphonates such as sodium dodecylbenzene sulphonate.
The compositions of the invention may be formulated as wettable powders5 dusts, granules, solutionsg emulsifiable concentrates, emulsions and pastes. Wettable powders are usually compounded to contain 25, 50 or 75% of toxicant and usually contain, in addition to solid carrler, 3-10%
of a dispersing agent and, where necessary, 0-10% of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant, and are dilute in the field with further solid carrier to give a composition usually containing 0.5-10% of toxicant.
Granules are usually prepared to have a size between 10 and 100 BS mesh~ and may be manufactured by agglomeration or impregnation techniques. Generally, granules will contain 0.5-25% toxicant and 0-25% of additives such as stabilisers, slow release modifiers, binding agents etc. ~mulsifiable concentrates usually contain, in addition to the solvent and, when necessary, co-solvent, 10-50~ w/v toxicant~
2-20% w/v emulsifiers and 0-20% of appropriate additives such as stabilisers, penetrants and corrosion inhibitors.

- 12 ~

Pastes are compounded so as to obtain a stable, flowable product and usually contain 10-60% toxicant, 2 20% of appropriate additives and, as carrier, water or an organic liquid in which the toxicant is substantially insoluble.
The compositions of the invention may contain other ingredients 3 for example protective colloids such as gelatin, glue, casein, gums and polyvinyl alcohol;
sodium polyphosphates; cellulose ethers~ stabilisers such as ethylene diamine tetra-acetic acid; other herbicides or pesticides; and stickers, for example, non-volatile oils.
A~ueous dispersions and emulsions, compositions obtained by d~uting a wettable powder or an emulsifiable concentrate according to the invention with water, also lie within the scope of the present invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick "mayonnaise"-like consistency.
The invention is further illustrated by reference to the following Examples:
Exam~e 1 Demons'tra'tion of herbicidal activity of N-sub-~1~ .
To demonstrate their herbicidal activity against broad-leaved weeds the compositions according to the invention Z5 were tested as foliar sprays on seedling plants of the following species: linseed, Linum us`i't'at'issi'mum (L);
mustardj ~ alba (M); sugar beet, Beta vulgaris (SB);
; and soya bean,' ~ max (S).

The for~ulations used in the test were prepared by diluting with water solutlons of the compounds in acetone containing 0.4% by weight o~ an alkylphenyl/ethylene oxide condensate available under the trade name Triton X-155.
The acetone solutions were diluted with an equal volume of water and the resulting rormulations applied at four dosage levels correspondlng to 0.1, 0.~, 1.0 or 3.0 kilograms of active material per hectare. There were ~ replicates of each treatment. Phytotoxicity was assessed visually 12 to 14 days after spraying the roliage, on the standard 0-9 scale. These phytotoxicity scores were submittecl ~or probit analysis to calculate the growth inhibition dosages in kg/ha required to give a 50% reduction (G I D50).

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H . . . . ~ .
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LOr~

m ~ t~ O
H ~-- ~ ~ ~. . .
O O O O
:
O
O O ~O
t~
~: ~ O O O O O ~\I
C~
L
~ ~ CO ~ CO ~1 ~S O 0 0 0 0 ~1 H ~ .
~ a ~
~ ~ 3 ~ ~
~d .
E~ ~ ~ ~, ~, o .

a X ~ ~ d ~ 0 X ~ ~ ~ s , 5 ~ o Q, a) ~ ~ S-~ Q~ 1 ::; o-~l o ~ o ~
O S~o ~ I O
Q O /1) 0 ~ O O O ~
: ~ ~-rl S ~ S ~ a o ~1 ~ ~ ~ C) a-r~ ~1 o V ~ ~ C~ + o ~ o I ~ I ~ O ~ o--~ ~ C) O
o a~ o ~ o ~ ~ ~ , O ~ O rR ~ ~ rl J~ O `
a~
I ~
=~ ~ I
I ~ I ~ rl ~ O
~s~S ~ ~~ ~ ~ ~ ~
rl ~ I a~I a) I ~ I ~ I ~ a :~ ~; ~z ~ z a~
:
'~ -`:

6~7 These ~igures also demonstrate that for a given compound the dextro-rotatory ~orm is mor~ herbicidally active than the racemic mixture.
Example 2 Demonstration of herbicidal activity of N substituted alanine compounds ~ . . ~ _ A second series of compounds were applied as foliar - sprays to soya bean at the cotyledon stage using the procedure described in example I and applying four dosage levels corresponding to 0.3, o.6, 1.2 or 2.4 10 kilograms of active material per hectare. Phytotoxicity was assessed 16 days after spraying and ~he G I D50 calculated.
Table 2 -Compound S

N-(3,4-dichlorophenyl)alanine isopropyl ester 0.12 (dextro-rotatory isomer) N-(3,4-dichlorophenyl)alanine ethyl ester0.07 (dextro-rotatory isomer) N-(3-chloro~4-fluorophenyl)alanine isopropylester 0.60 (dextro-rotatory isomer) N-3-chloro-4-fluorophenyl)alanine methyl ester o.80 (dextro-rotatory isomer) Example 3 of N-substituted' alani'ne c'ompounds .
TG demonstrate their selective herbicidal action (in ~ controlling the growth of broad-leaved weeds in barley ; crops) the compositions according to the invention were ~ lfi -tested as foliar sprays on seedling plants of th~
following species: mustard, ~ alba (M); soya bean, Glycine max (S); convolvulus, Ipo~ea (I) and barley, Hordeum vulg re (B).
The formulations used in the test were prepared as in Example I. Two tests were carried out.
Test I The compounds were applied post-emergence to soya bean, mustard and barley at 4 dosages: Barley from 3 to 24 kg/ha; soya bean and mustard from 0.2 1~ to 1.6 kg/ha. There were 4 replicates of each treatment.
Phytotoxicity was assessed visually on the standard 0-9 scale, 8 days after spraying. This data was analysed by computer to calculate the growth inhibition dosages required to give a 50% reduction for barley, soya bean and mustard. The results are given in Table 3.
Table 3 Compound G I D50 G I D50 G I D50 N-(3-chloro-4-fluorophenyl) ~20 2.89 o.69 alanirie N-~3-chloro-4-fluorophenyl) 16.3 0.93 o.65 alanine methyl ester (racemic ~ mixture) ; Test 2 The compounds were applied to soya bean, convolvulus and barley at 4 dosages: Barley from ll to 32 kg/ha and soya bean and convolvulus from 0.3 to 2.4 kg/ha. ~here were 3 replicates of each treatment.

17~ 6~7 Phytotoxicity was assessed visually on the standard 0-9 scale 14 days (for barley) and 22 days (for soya bean and convolvulus) after spraying. The G I D50's obtained from this data are shown in Table 4.

Table 4 ~

Compound G I D50 G I D50 G I D50 N-(3-chloro-4-fluorophenyl)alanine 11~7 1.28 1.60 isopropyl ester (racemic mixture3 N-(3-chloro-4-fluorophenyl)alanine 11.2 0.92 o.g8 isopropyl ester (+ isomer) Example 4 Demons'trat'ion o.f synergi'stic' h_rb'i'c'i'dal acti'vity ''o'f mixt'ures''o'f N-s~ub's~ti~t~ut'ed'and' N,N-d'is'ubst'ituted _ _ _ _ alenines ; The miYtures under test in this example were as follows:
Mixtur'e I N-Benzoyl-N-(3,4-dichlorophenyl)alanine ethyl ester (A) and N-(3,4-dichlorophenyl)alanine ethyl ester (B) Mixture 2 N-Benzoyl-N-(3-chloro-4-fluorophenyl)alanine methyl ester (C) and N-(3-chloro-4-fluorophenyl)alanine methyl ester (D).
Mixture 3 N-BenzoyI-N-(3-chloro-4-fluorophenyl)alanine methyl ester (C) and N-(3-chloro-4-fluorophenyljalanine (E)~
ixture'4 N-Benzoyl-N-(3-chloro-4-fluorophenyl)alanine methyl ester (-isomer) (F) and N-(3-chloro-4-fluorophenyl) alanine methyl ester (+ isomer) (G).
~ , .

Mixture 5 N-Benzoyl-N-(3-chloro-4-fluoro~henyl)alanine methyl ester (-isomer) (F) and N-(3~4-dichlorophenyl) alanine ethyl ester (+ isomer) (H).
All compounds were formulated as 15-20% emulsifiable concentrates. The dosages used for com~ound (A) were 0,04, o.o8, 0.16 or 0.32 kg/ha and for compounds (C) and (F) 0.02, 0.04, o.o8 or 0.16 kg/ha. Sufficient amounts of the five compounds of the invention were added to produce mixtures with the required ratios. These five compounds (i.e. B, D, E, G, and H) were also applied alone at high dosages and were found ko be inactive against cultivated oats at the dosages given in the test.
A number of 7 ~m pots o~ John Innes No. 1 Compost were sown with 25-30 seeds of cultivated oats (Avena sativa). When the plants had reached the l-lz leaf stage mixtures of different ratios of the compounds were sprayed using a lo~arithmic sprayer. Assessments were made 10 to 15 days after spraying according to the mixture. Phytotoxicity was assessed visually on a percentage scale (where 0 = no effect and 100 = no growth after spraying). The data was analysed to calculate the growth inhibition dosages in kg/ha required to give a 90% reduction for oat (G I Dgo).
Results of these mixture tests are given in Table 5.

- 19~ 5~
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O ~
o o o o ~ ~ 6, o o o o ~ td ~
IA ~ _ o o ~ o o ~ ~ =r ~-rl .X o ~ .. .. .. .. .. .. ..
o o -~D ~ Lt~ Lr~ ~
o o o H O O O O O
~ ~ :
_ . ~

O O CS O ~ 1 P.~rl X ~ ...... .. .. .. .. .. ..
~r~ O ~
O S~ ¢~ t\l rl ~1 ~1 0 O
u~ ~ c~ o H ~ ~1 ~1 0 ~1 ~ ' . . . . I
C~ O O O O O
1~ - ~
a~ ~:
~ ~ 0~ O O ~ ~ ~ .' ~ Q~ri ~ o3~ ..........
~ O ~ ~ ~1 ~1 ~1 ~1 0 a~ .- .
r~ cO
P ~ ~ ~ Lr~
~d H ~ O O O O O
E~ ~d .
C~ O O O O O O
,, _ _ _ :~ ~0 0 ~ O ~ ~ ~ CO
p,-rl , X ~ .. .. .. .. .. .. ..
~1 O td C~ ~ V ~1 ~1 ~1 ~1 ~1 o -~ --.
n :
u~ ~ ~ ~ ~r H ~ ~J ~1 ~1 ~1 (~
O o o o o o ~_ .
~:
o om o ~ ~1 ~ ~ ~ :
L~-rl X ~ .. .. .. .. .. .. ..
~1 o ~
~ . = ~_ Example 5 The mixture under test in this example was as follows N-Thiobenzoyl N-(3~chloro-4-fluorophenyl)alanine isopropyl ester (.A) and N-(3-chloro-4-fluorophenyl)alanine isopropyl ester (B).
The test procedure was the same as that given in Example 4.
The dosages used for compou~d (A) were 0.24, o.48, or o.g6 kg/ha with sufficient amounts of the compound of the invention added to give mixtures with the required ratios.
Visual assessments were made 19 day.s after spraying and G I Dgo calculated as for prevlous tests.
Results o~ the test are given in Table 6, Table 6 .
_ . _ .
Compound ratio oGat Dgo - -- - ~
, 1: 0 0.99 1: 1 0.91 1 : 2 0.73 1 : 4 o.60 0 : I . _ .
.~
.' , .

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Herbicidally active compositions which comprise a carrier and/or a surface-active agent and as active ingredient at least one N-substituted alanine compound having the general formula:

(I) wherein X is a fluorine or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z is a hydrogen atom or a C1-6 alkoxy group; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group con-sisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -SR2 in which R2 is an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy or with the proviso that if Z is hydrogen, and both X and Y are chlorine, then R1 is other than hydrogen.

2. A composition according to claim 1, wherein the active ingredient is an N-substituted alanine compound with the general formula:

(II) where X is fluorine or chlorine, Y is chlorine, R is a hydrogen atom or an alkyl group of 1 to 4 carbon atoms.

3. A composition according to claim 2, wherein R is a methyl, ethyl or isopropyl group.

4. A composition according to claim 1, wherein the N-substituted alanine compound is present in the dextro-rotatory form.

5. Herbicidally active compositions which comprise a carrier and/or a surface active agent, and as active ingredients at least one N-substituted alanine compound chosen from each of the following groups:
(a) a compound of the general formula:

(I) wherein X is a fluorine or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z is a hydrogen atom or a C1-6 alkoxy group; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consist-ing of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -SR2 in which R2 is an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substi-tuents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy;
(b) a compound of the general formula wherein Y is hydrogen, fluorine or chlorine; X is chlorine or fluorine Q

is oxygen or sulphur; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; a group of formula -SR2 in which R2 is an optionally substitu-ted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consist-ing of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -NR3R4 or -ON=CR3R4 in which R3 and R4 each individually is hydrogen, hydroxy, an optionally substituted C1-6 alkyl, C1-6 alkenyl, C1-10 aryl, C1-10 alkaryl, C1-10 heterocyclyl, C1-6 alkoxy, C1-6 alkylthio or amino group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy, or R3 and R4 together repre-sent a polymethylene group optionally interrupted by one or more hetero atoms selected from the group consisting of oxygen, nitrogen and sulphur.

6. A composition according to claim 5, wherein the N,N-disubstituted alanine compound has the general formula:

(IV) wherein X and Y each individually represent chlorine or fluorine and R is a hydrogen atom or an alkyl group containing up to 6 carbon atoms.

7. A composition according to claim 6, wherein X is fluorine, Y
is chlorine and R is isopropyl.

8. A composition according to claim 6, wherein X is chlorine or fluorine, Y is chlorine and R is methyl or ethyl.

9. A composition according to claim 5, wherein the N,N-disubstituted alanine compound is present in the laevo-rotatory form.

10. A composition according to claim 5, wherein the N-substituted alanine compound of the general formula (I) as defined in claim 5 is present in the dextro-rotatory form and the N,N-disubstituted alanine compound of formula (III) as defined in claim 5 is present in the laevo-rotatory form.

11. Method of controlling broad-leaved weeds which comprises applying to the weeds or their habitat a herbicidally effective amount of an N-substituted alanine compound of formula I

(I) wherein X is a fluorine or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z is a hydrogen atom or a C1-6 alkoxy group; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consist-ing of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -SR2 in which R2 is an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional sub-stituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy.

12. A method of controlling both broad-leaved weeds and grass weeds infesting cereal crops which comprises applying in combination to the weeds or their habitat a herbicidally effective amount of at least one N-substituted alanine compound chosen from each of the following groups:

(a) a compound of the general formula (I) wherein X is a fluorine or chlorine atom; Y is a hydrogen, fluorine or chlorine atom; Z is a hydrogen atom or a C1-6 alkoxy group; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consist-ing of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -SR2 in which R2 is an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional sub-stituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; and (b) a compound of the general formula:

(III) wherein Y is hydrogen, fluorine or chlorine; X is chlorine or fluorine; Q
is oxygen or sulphur; and R is a group of formula -OR1 in which R1 is hydrogen, a metal salt-forming or an optionally C1-6 alkyl substituted ammonium ion, an optionally substituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; a group of formula -SR2 in which R2 is an optionally sub-stituted C1-6 alkyl, C1-10 cycloalkyl, C1-10 aryl, C1-6 alkenyl or C1-10 alkaryl group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy; or a group of formula -NR3R4 or -ON=CR3R4 in which R3 and R4 each individually is hydrogen, hydroxy, an optionally substituted C1-6 alkyl, C1-6 alkenyl, C1-10 aryl, C1-10 alkaryl, C1-10 heterocyclyl, C1-6 alkoxy, C1-6 alkylthio or amino group wherein the optional substituents are selected from the group consisting of chlorine, fluorine, C1-4 alkyl and C1-4 alkoxy, or R3 and R4 together represent a polymethylene group optionally interrupted by one or more hetero atoms selected from the group consisting of oxygen, nitrogen and sulphur.

13. A method according to claim 11 or 12, wherein the compound of formula I as therein defined is present in the dextro-rotatory form.

14. A method according to claim 12, wherein the compound of formula I as defined in claim 13 is present in the dextro-rotatory form, and the compound of formula III as defined in claim 12 is present in the laevo-rotatory form.

15. A method according to claim 11, wherein is used an N-substituted alanine of formula II

(II) where X is fluorine or chlorine, Y is chlorine, R is a hydrogen atom or an alkyl group of 1 to 4 carbon atoms.