US 3762423 A
Methyl trans-2-isopropyl-5-methyl-3-hexenoate and certain of its derivatives such as the corresponding alcohol, aldehyde, or carboxylic acid enhance the flavor of the mainstream of cigarette smoke and are useful as flavorants for all modifications of tobacco and tobacco products.
Description (OCR text may contain errors)
United States Patent 1 1 Simpson et a1.
1 1 Oct. 2, 1973 METHYL TRANS-Z-ISOPROPYL-S-METHYL-3- HEXENOATE AND DERIVATIVES THEREOF AS TOBACCO FLAVORANTS  Inventors: Melvyn 1. Simpson; Albert 11.
War-field; Andrew G. Kallianos, all of Durham, N.C.
 Assignee: Liggett & Myers Incorporated, New
1970, abandoned, and a continuation-in-part of Ser. No. 153,900, June 16, 1971, Pat. No. 3,704,714.
 US. Cl. 131/17 R, 99/140  Int. Cl.... A24b 15/00 [58} Field of Search 131/17 R, 144;
 References Cited UNITED STATES PATENTS 2,995,476 8/1961 Hind 131/17 R 3,047,433 7/1962 Bauley 131/17 R 3,111,127 11/1963 .Iarboe 131/17 R 3,174,485 3/1965 Griffith 131/17 R 3,381,691 5/1968 Schumacher... 131/144 X 3,449,407 6/1969 Theimer 131/17 X 3,704,714 12/1972 Kallianos et a1. 131/17 R Primary ExaminerRobert W. Michel] Assistant Examiner-George M. Yahwak Att0rneyEdward W. Greason  ABSTRACT Methyl trans-2-isopr0py1-5-methy1-3-hexenoate and certain of its derivatives such as the corresponding a1- cohol, aldehyde, or carboxylic acid enhance the flavor of the mainstream of cigarette smoke and are useful as flavorants for all modifications of tobacco and tobacco products.
9 Claims, No Drawings METHYL TRANS-Z-ISOPROPYL-S-METHYL-3-HEXENOATE AND DERIVATIVES THEREOF AS TOBACCO FLAVORANTS This application is a continuation in part of Ser. No. 5 806,682, filed Mar. 12, 1969, now abandoned, and a continuation in part of Ser. No. 57,414, filed June 19, 1970, now abandoned, and a continuation in part of Ser. No. 73,194, filed Sept. 17, 1970, now abandoned, and a continuation in part of Ser. No. 153,900, filed June 16, 1971 now U.S. Pat. No. 3,704,714.
This invention relates to novel unsaturated acids, esters, alcohols, aldehydes and ketones having utility as flavorants. More particularly, this invention is concerned with compounds containing the trans-2,6- dimethyl-3-hepten-5-yl group which have utility as additives to modify the taste of tobacco.
The compounds ofthis invention are transunsaturated compounds of the formula (CH;) CHCH=CH( JHCII(CH wherein X is an oxygen-containing radical bonded to the hydrocarbon chain through a carbon atom which is bonded directly to oxygen.
The radical X may be further represented by the radicals wherein R is hydrogen, lower alkyl, hydroxy or lower alkoxy, or
(A) ZCO -lower alkyl ll-H l Z-GHO ZCH OII Li lower alkyl Z-CH-lower alkyl Z-C-lower alkyl wherein Z is the trans-2,6-dimethyl-3-hepten-5-yl group. Other compounds of this invention are obtained through conversions of esters (B) to the free acid or conversions of the alcohols to their esters.
All of these reactions may be effected through known techniques. For example, the compounds wherein X is carboalkoxy, i.e., the lower alkyl trans-2-isopropyl-5- methyl-3-hexenoates, are obtained by dehydration of the corresponding lower alkyl 2-isopropyl-3-hydroxy- S-methylhexanoate over phosphorus pentoxide in benzene. The product can be isolated by distillation from the reaction mixture at reduced pressure. The free acid is readily obtained through saponification of the ester and acidification to yield trans-2-isopropyl-5-methyl-3- hexenoic acid.
The compound wherein X is hydroxymethyl, i.e. trans-2-isopropyl-5-methyl-3-hexenol, (C) can be obtained by reduction of, e.g., methyl trans-2-isopropyl-5- methyl-3-hexenoate. The preferred method of reduction is treatment of the ester by an ether solution of lithium aluminum hydride. Esters of the alcohol may be obtained via conventional techniques.
The product in which X is formyl, trans-2-isopropyl- 5-methyl-3-hexenal, is obtained by oxidation of the corresponding alcohol (C), preferably by a solution of chromic acid-pyridine complex in methylene chloride solution. This product can be isolated and purified by gas-liquid partition chromatography.
Treatment of trans-Z-isopropyl-S-methyl-3-hexenal (D) with an ethereal solution of methyl lithium produces trans-3-isopropyl-6-methyl-4-hepten-2-ol, which can be isolated and puri-fied by gas-liquid partition chromatography. In an analogous manner, other a -hydroxyalkyl derivatives can be obtained through the use of other lower alkyl'lithium compounds. All of the alcohols can be converted to their lower acyl esters in known manner.
Finally, the compounds where X is acyl (F), such as trans-3-isopropyl-6-methyl-4-hepten-2-one, are obtained via oxidation of the corresponding a-hydroxyalkyl compounds (E), preferably with chromic acidpyridine complex in methylene chloride solution. These products can be isolated and purified by gasliquid partition chromatography.
It will be readily apparent to those experienced in the art that the above methods of preparation'are intended only to be illustrative and not exclusive, and that the products may be obtained by other methods, both chemical and catalytic. v
The compounds of this invention are usefulto modify the flavor of tobacco products, and are-especially useful as cigarette flavorants. They may be applied to tobacco or reconstituted tobaccosheet by spraying in a suitable solvent such as ethanol, propylene glycol, glycerine, or casing solution, by dipping into a solution containing the appropriate products, or by incorporation into a flavor formulation normally applied to tobacco or reconstituted tobacco sheet. The concentration of the flavorant in the tobacco is not narrowly critical, and will vary depending upon the compound and the effect desired. However, the concentrations normally will be in the range of from about 0.001 to about 0.01 weight per cent, based upon the weight of the tobacco or reconstituted tobacco sheet, although higher and lower concentrations may be employed if desired.
The following examples illustrate the preparation and spectral characteristics of the compounds of this invention.
EXAMPLE 1 Methyl trans-2-1sopropyl-5-methyl-3-hexenoate A mixture of 10 g of phosphorus pentoxide in 20 ml. of anhydrous benzene was cooled to 10". Twenty grams (0.099 m) of methyl 2-isopropyl-3-hydroxy-5- methylhexanoate was added dropwise with stirring over three-fourths hr. The mixture was stirred an additional one-half hr. at room temperature and then distilled. The benzene was removed at about 25-30 mm. pressure and the product was distilled at 59-61/1-2 mm; yield 14.4 g. (79%);kmax 3.31 (vinyl C-H), 5.76
EXAMPLE v trans-3-lsopropyl-6-methyl-4-hepten-2-one trans-3-lsopropyl-6-methyl-4-hepten-2-one was synthesized from the corresponding alcohol by oxidation with a methylene chloride solution of chromic acidpyridine complex (R. Ratcliffe and R. Rodehorst, loc. cit.);kmax" 5.85 (C=O), 7.21 and 7.31 (isopropyl), and 10.25 p. (-HC=CHtrans); mass spectrum M 3:0 720- and 729 (isopropyl), and 1017 10 at m/e 168;NMR spectrum was in agreementwith pro- (HC=CH trans); mass spectrum M at m/e 184;? Structure- NMR spectrum was consistent with proposed structure.
EXAMPLE ll trans-2-lsopropyl-5-methyl-3-hexen-l -ol A slurry of 0.76 g. (0.02 m) of lithium aluminum hydride in 25 ml. of anhydrous ether in a 250-ml., 3- necked flask was cooled to A solution of g. (0.0272 m.) of methyl trans-2-isopropyl-5-methyl-3- hcxenoate in 25 ml. of anhydrous ether was added dropwise with stirring. The reaction mixture was stirred an additional 15 min. at 0, then for 2 hrs. under reflux.
The mixture was cooled to 0 and hydrolyzed by dropwise addition with stirring of 18 ml. of percent sulfuric acid. The layers were separated and the ether layer was washed with water (twice) and saturated sodium chloride solution, dried over sodium sulfate, and evaporated on the rotary evaporator. The product was purified by molecular distillation at 20-30 mm. pressure and a block temperature of 90l00; kmax 2.75 and 2.80 (OH), 7.20 and 7.30 (isopropyl). 9.44 (CO), and 10.21 p. (l-1C=CH trans); mass spectrum-M at m/e 156; NMR spectrum corresponded to structure.
EXAMPLE lll trans-2-lsopropyl-5-methyl-3-hexenal trans-2-Isopropyl-5-methyl-3-hexen-l-ol was oxidized to the corresponding aldehyde with a solution of chromic acid-pyridine complex in methylene chloride solution according to the published procedure [R. Ratcliffe and R. Rodehorst, J. Org. Chem., 35, 4000 (1970)];kmax" 3.57 and 3.71 (CljO), 5.80 (C=O), 7.21 and 7.30 (isopropyl), and 10.26 p. (HC=CH trans); mass spectrum M at m/e 154; NMR spec- I trum was consistent with structure of title compound.
2,4-DNP m.p. l41-142. Anal. Calc. for C I-1 N 0 C, 57.57; H, 6.63; N, 16.76. Found: C,57.63; H, 6.80 N, 16.88.
EXAMPLE 1V trans-3-lsopropyl-6-methyl-4-hepten-2-ol One gram of trans-2-isopropyl-5-methyl-3-hexenal dissolved in 50 ml. of anhydrous ether was treated with 6 ml. of 1.66 M ethereal methyl lithium at approximately 10 under an atmosphere of nitrogen. After addition was complete, the reaction solution was stirred under reflux for 1.5 hrs., cooled to 0, and hydrolyzed by dropwise addition of 10 ml. of percent sulfuric acid. The layers were separated and the organic layer was washed with saturated sodium bicarbonate solution, water, and saturated sodium chloride solution, dried over sodium sulfate, and evaporated on the rotary evaporator; )lmax 2.81 (OH), 7.21 and 7.31 (isopropyl), and 10.23 p. (HC=CH-- trans); mass spectrum M at m/e 170.
EXAMPLE Vl Aliquots of 10 ;/.l. of a solution of 10 mg. of each of the products of Examples l-V dissolved in 1 ml. of percent ethanol were injected uniformly along a path of 55 mm. length in experimental cigarettes manufactured from a commercial blend of tobaccos. The solvent was removed from each cigarette by evaporation at room temperature.
The smoke and flavor characteristics of each sample were evaluated by an experienced flavor panel. The samples were compared to control cigarettes prepared identically to the sample cigarettes but without the flavor additives.
Cigarettes prepared as described above containing methyl trans-2-isopropyl-5-methyl-3-hexenoate (Example 1) produced smoke which exhibited increased sweetness and fullness and enhanced fragrance and tobacco character.
Cigarettes treated with trans-2-isopropyl-5-methyl-3- hexen-l-ol (Example 11) produced smoke exhibiting an increase in green character and a slight increase in tobacco character.
trans-2-isopropyl-5-methyl-3-hexenal (Example [11) treated cigarettes produced a smoke flavor described as weedy green and burnt woody with a slight increase in Turkish character.
The smoke from cigarettes containing trans-3- isopropyl-6methyl-4-hepten-2-ol (Example 1V) exhibited less dirty notes and pepperiness with improved flavor balance.
Cigarettes containing trans-3-isopropyl-6methyl-4- hepten-2-one (Example V) produced a smoke flavor with increased green and bitter'character and an increase in natural sweetness.
What is claimed is:
1. A tobacco composition including at least one compound of the formula:
X l (CllahUllCll CllUllC(011 wherein X is an oxygen-containing radical of the formula wherein R is hydrogen, lower alkyl, hydroxy or lower alkoxy, R is hydrogen or lower acyl, and R" is hydrogen or lower alkyl wherein the amount of said comhydroxymethyl.
6. A composition according to claim 1 wherein X is formyl.
7. A composition according to claim 1 wherein X is a-hydroxyethyl.
8. A composition according to claim 1 wherein X is acetyl.
9. A tobacco smoking article including a tobacco composition according to claim 3. l III UNITED STATES, PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. '3,762 l23 I Dated 10/2/73 lnventofls) Melvyn T. Simpson Albert H- Warfie'ld and Andrew G. Kallianos It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 2, line 28, correct spelling of "purified".
Column 6 claim 9, line 10, change dependency of claim from claim 3 to claim l.
Signed and sealed this 23rd day of A ril 197i.
EDWAl'iD I LFLETCI-IEILJR. C I IARSHALL DANN Attesting Officer Commissioner of Patents