Note: Descriptions are shown in the official language in which they were submitted.
~036611
CIS-Z~R~LENE ~ND R~LATED COMPOUND~
This invention relates to a process of making cis
isomers of compounds represented by the formula
~ 8 IH3
R2 ~ H~
/ 2 ~ H
C~ I '~
CH2 CH2
wherein Z is \ C=O or ~ C or ~ C < and each of Rl and
R2 can be hydrogen~substituted and unsubstituted alkyl, e.g.,
containing from about 1 to 15 carbon atoms including lower
alkyl such as methyl, ethyl, hexyl, etc., and cycloalkyl such
as cyclopentyl,cyclohexyl, etc.; alkanoyl, generally containing
about 1 to 25 or more carbon a~om~ including lower alkanoyl
such as acetyl, valeryl, propionyl, etc.; substituted or
unsubstituted aryl, for instance, monocyclic aryl containing
about 5 to 10 carbon atoms or more such as phenyl, for instance;
aryl alkyl (that is an alkyl group having an aryl substituent
thereon), the aryl ~ubstituent may be monocyclic aryl contain-
ing about 5 to 10 carbon atom~ or more and the alkyl group is
generally lower alkyl, for example, one to about slx carbon
atoms, such as benzyl, bromobenzyl, and the like, Rl and R2
being the same or different with the proviso that when both
Rl and R2 are hydrogen, Z i/ C ~ . These compounds are
advantageously produced from their respective trans i~omers by
irradiation with electromagnetic radiation having a wavelength
~, ..
~Q36611
of about 2800 to 3500 angstroms. The cis compounds of this
invention can be produced essentially pure, e.g., generally
above about 90 percent, often above about 97 percent pure.
Because of the ethylenic unsaturation between the 1
and 2 position carbon atoms in the lactone ring, the compounds
prepared in accordance with this invention can theoretically
exist in two stereoisomeric forms: cis and trans. The compound
zearalene (also known as 6-(10-hydroxy-1-undecenyl)-B-
resorcylic acid-~-lactone) exhibits estrogenic activity and
aids in increasing the rate of growth in meat producing animals.
Zearalene may be prepared by the reduction of the keto group of -
zearalenone to replace the oxygen of the keto group with two ~;
hydrogen atoms. This reaction is described, for example, in
U.S. Patent No. 3,239,341 to Hodge et al.
;. :.
One or both of the hydroxy substituents on the benzene
ring of zearalene may undergo replacement of the hydrogen atom
with an alkyl, alkanoyl, aryl, or aryl alkyl radical. Con-
ventional processes for the hydrogen replacement reaction may
be employed and are illustrated, for instance, in U.S. Patent
Nos. 3,239,341; 3,239,342; 3,239,347; 3,239,348; and 3,373,039
to Hodge et al.
It is realized that, for instance, cis zearalene
may be prepared by the appropriate reduction of the keto group
,~ .
in cis-zearalenone to an alcohol group of hydrogens. Similarly, -
the hydrogen atoms of the hydroxy groups on the benzene ring of
a cis compound may be replaced to provide the desired cis-
derivative.
Identification of the cis isomers can be by nuclear
magnetic resonance spectroscopy (nmr). For instance, whereas
the proton on the 1 position lactone ring carbon atom in trans-
zearalenone exhibits an absorption at 7.14~, in cis-zearalenone
'.' '~
-2
1~36Gll
~t exhibits an absorption at only 6.72~. The coupling constant,
J, between the 1 and 2 position lactone ring carbon atoms is 16
Hz in the trans isomer and only 11.5 Hz in the cis isomer. As ~r
regards zearalene, similar differences in the nmr absorption of
the protons on the 1 and 2 position lactone ring carbon atoms
are found between the cis and trans isomers.
The irradiation of the trans isomers to produce the
cis-isomers of this invention can be carried out with an ultra-
violet irradiation source which can produce a wavelength
10 generally in the range of about 2800 to 3500 angstroms. The `
irradiation dosages in these wavelengths may often be at least
about 10 kwh./hr./kg. of starting material, preferably about -
20 to 500 kwh./hr./kg. of starting material. The length of time
that the trans isomer is exposed to the irradiation can vary
widely depending upon such factors as the amount of trans isomer,
the irradiation wavelength, dosage, etc. Generally, the
irradiation is continued for a period of about 1 to 200 or more
hours and preferably for a period of about 6 to i20 hours.
Typical sources of ultraviolet irradiation which can
be used in the present process include mercury vapor lamps,
carbon arc lamps, and tungsten arc lamps.
The irradiation is preferably effected with the trans
isomers in solution in a stable solvent, i.e., one which is
non-reactive with the starting material and product under the
irradiation conditions. Suitable solvents include lower mono-
hydric alkanols, acetonitrile, and dichloromethane. Methanol
is preferred. Preferred solution concentrations are about 0.5
to 2.5, most preferably about 1 to 2, weight percent.
It is also preferred that the trans isomer be
essentially free from contact with oxygen during the irradiation,
the reason being that oxygen might possibly inhibit the
- . - : : ~ .
1~36~i11
stereoisomerization and/or oxidize the reactants. Where
solution irradiation is employed this can be achieved, for
example, by first purging the solution with an inert gas such as
nitrogen, argon or helium and then maintaining the solution in
an atmosphere of inert gas during the irradiation.
The maximum amount of cis isomer that can be obtained
in the product of the photochemical process of this invention
is generally above 90 percent, e.g., approximately 97 percent.
Suitable solvent systems for the recrystallization include lower ~ -
monohydric alkanol/water mixtures such as methanol/water mixtures
and isopropanol/water mixtures. Most preferred is a methanol/
water mixture containing about 20 to 50 volume percent water.
The crude cis-zearalene product may conveniently be
recrystallized from benzene to upgrade purity. It is generally `-
advantageous to treat product solutions of cis isomers with
activated charcoal so as to enhance the purity of the product.
The irradiation is preferably continued until the ;
cis/trans isomeric mixture contains at least about 90 percent,
or even at least about 95 percent, of the cis isomer.
Slightly elevated, room, or lowered temperatures (e.g.,
about 15-45C.) and superatmospheric, atmospheric, or sub-
atmospheric pressures can be used for the stereoisomerization
reaction of the present invention. For reasons of economy,
however, it is preferred to operate under ambient conditions,
i.e., at room temperature and atmospheric pressure.
The alternative method of producing cis-zearalenol
derivatives is by reducing the ketone group of the corresponding '
cis-zearalenone derivative, reducing conditions of temperature
and pressure in the presence of a suitable reducing agent and ~
30 is also preferably carried out in solution in a stable solvent, -
e.g., dimethylformamide, tetrahydrofuran, or a lower monohydric
1036611
alkanol, such as isopropanol, methanol or ethanol. Preferred
solution concentrations are about 5 to 10 weight percent.
Any reducing agent which is selective for the ketone
group and unreactive with the solvent can be employed in the
reaction. Most preferred is a borohydride such as sodium
borohydride and potassium borohydride. The latter should not
be used, however, in conjunction with an alcohol solvent. These
borohydride reducing agents are advantageously employed in an
amount which is at least equimolar to the amount of cis-
zearalenone.
Subatmospheric, atmospheric, or superatmosPhericpressures can be used for the reduction reaction, with atmos-
pheric pressure being preferred for economic reasons. The
temperature to be employed will depend upon the choice of
reducing agent and solvent but will generally be about 15 to
45C.
The alternative method of producing cis-zearalene or
derivative thereof is by the reduction of the ketone group of
cis-zearalenone or corresponding derivative of cis-zearalenone,
to replace the oxygen of the ketone group with two hydrogen
atoms. The reduction of the ketone group can be effected by
several procedures. One of these procedures involves the
Clemmensen reaction using zinc and hydrochloric acid; another
involves the Wolff-Kishner reaction using hydrazine and alkali,
e.g., sodium hydroxide.
Cis-compounds wherein the substituents on the benzene
ring are hydroxyl groups, may be converted to compounds in
which one or both of Rl and R2 are alkyl, alkanoyl, aryl, or
aryl alkyl. In producing the compounds of the present invention
where R is alkyl, conventional alkylation procedures may be
used to replace the hydrogen atom of one or both of the hydroxyl
~0366~
groups on the benzene ring with an alkyl group. The alkylation
may be by reaction with the corresponding dialkyl sulfates,
e.g., dimethyl sulfate, diethyl sulfate, etc., to produce a -;
dialkyl substituted or a monoalkyl substituted compound with
the alkyl group replacing the hydrogen of the hydroxyl group
ortho to the ester group. The alkylation reaction may take
place in a liquid medium such as water. Furthermore, a methyl
group may selectively replace the hydrogen of the hydroxyl
group para to the ester group on the benzene ring using diazo-
methane.
The hydrogen atom hydroxyl substituents on the ~ -
benzene ring may be replaced by a carbon-containing, cyclic
group by a condensation reaction in a slightly alkaline, - -
organic solvent medium with the corresponding acid anhydride
or chloride of the cyclic compound. Illustrative of cyclic ~ -
substituents, alkyl and aryl or aryl alkyl, are benzyl, bromo- - -
benzyl, benzothiazolyl, phenyltetrazolyl, benzoxazolyl, tetra-
hydrofuranyl, tetrahydropyranyl, cyclopentyl, cyclohexyl,
naphthyl, etc.
Where R is desired to be alkanoyl, conventional
acylation procedures may be used to replace the hydrogen atom
of both the hydroxyl groups on the benzene nucleus with an
alkanoyl radical. For instance, acylation may be effected by
reaction with the corresponding acid anhydride, e.g., acetic
anhydride, propionic anhydride, etc., catalyzed with, for
example, sodium acetate or pyridine. Ambient conditions may be -
employed although it is preferred to keep the reaction mixture
cold.
The cis isomers of the present invention can be
administered to animals by any suitable method, including oral
and parenteral administrations or as an implant. For example,
1036~i1i
the compounds can be blended with ordinary feed which contains
nutritional values in an amount sufficient to produce the
desired rate of growth and thus be fed directly to the animals,
or the compounds can be suspended in a suitable injection
suspension medium, such as peanut oil, and injected parenter- -
ally. The amount of compound fed to an animal varies, of
course, upon the animal, the desired rate of growth, and the
like. In general, from 2.5 to 50 grams of the compound per
ton of feed is typical. When an implant is used, for example
a ball or cylindrical implant inserted under the skin on the
ear of an animal, e.g., a lamb or steer, the implant will
generally contain from 1 mg. to 100 mg, of the compound.
When an isomer of this invention is to be administered
to animals in their feed, an animal feed composition may be
prepared containing the usual nutritionally-balanced quantities
of carbohydrates, proteins, vitamins, and minerals together
with the isomer. Some of the usual sources of these dietary
elements are grains, such as ground grain and grain by-products;
animal protein substances, such as those found in fish meal
and meat scraps; vegetable proteins, such as soybean oil meal
or peanut oil meal; vitaminaceous materials, e.g., vitamins
A and D mixtures; riboflavin supplements and other vitamin B
complex members; and bone meal and limestone to provide
minerals. A type of conventional feed material for use with
cattle, for example, includes alfalfa hay and ground corn
cobs, together with supplementary vitaminaceous substances if
desired.
EXAMPLE I
".
This example illustrates the preparation of cis-
zearalene from trans-zearalene in accordance with the method
of this invention. One gram of trans-zearalene is dissolved -
1036611
in 500 milliliters of methanol, and the solution is placed in a
500 milliliter photochemical reactor (Ace Glass Model 6515) ~ -
equipped with a borosilicate glass immersion well (Ace Glass
Model 6517-05). The solution is purged with nitrogen for
about 12 hours and is then irradiated under a nitrogen atmos-
phere with a 450-watt, medium pressure, mercury vapor lamp --
(Ace Glass Model 6515-34) for 24 hours. The resulting solution
is evaporated to dryness under vacuum on a rotary evaporator and
the residue is recrystallized from benzene to give 0.70 gram of
cis-zearalene as white crystals having a melting point of 143
to 145C. Analysis indicates the presence of 70.67 weight
percent carbon and 8.27 weight percent hydrogen, as compared
with theoretical values of 71.05 weight percent carbon and 7.89
weight percent hydrogen. ~
EXAMPLE II ;-
Samples of cis-zearalene are tested for uterotropic `-
activity according to the well known mouse uterine test. This
test consists of feeding the test compound in a sesame oil
carrier to ten, adult, ovariectomized female mice for three
20 days at a ration of 50, 100, and 300 micrograms of compound
per mouse per day. On day four the animals are sacrificed, and
the uteri are removed and weighed. The test result~ are
reported in Table I.
:
`
36611
TABLE I ~ -
Test Total Uterine ~ Body
Compound Dose (~g) Weight (mg) Weight
Control ---- 10.3 0.041
Trans-zearalenone 300 26.2 0.100
Trans-zearalene 300 16.2 0.066
900 18.1 0.070
Cis-zearalene 150 22.6 0.087
300 30.3 0.120 ~
900 48.6 0.188 ~ -
EXAMPLES III to X
Essentially the same procedure used in Example I is
followed to prepare cis isomers of compounds of the general
formula
R2Ol~
CH2
\~H2--CH2
wherein the values of Rl, R2 and Z are set forth below for the
respective examples from the corresponding trans isomers where-
in the values for Rl, R2 and Z are the same as in the product.
~ . , .
The starting compounds can be produced in accordance with the
above-identified United States Patents issued to Hodge.
i .
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:,
. ~
_g_ :~
,, ., . ., .. ,. ... ~ . , . ~ . .. .
~ t
1l~36611
: EXAMPLE R R Z
III -CH3 -CH3 ~ CH2
IV -CH2CH3 -CH2CH3 > CH2
: . -
V -C-CH3 -CH3 >CH2 ~
. VI -CH3 -CH3 > CHOH :
` VII -H benzyl > C=O ;
- VIII -H bromobenzyl ~ C=O : `:
, ' ' ~ '~
10 IX -CH3 -C-CH3 > CH2 ;
:- o
-C-C4Hg -C-C4Hg > C=O
-~ a feed mixture is prepared from each of the above compounds
having 10 ounces of the cis isomer per one hundred pounds of . :~
mixture comprising alfalfa hay and ground corn cobs and is -~
used to feed in daily ration portions six head of cattle.
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- 1 O-
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