Patented Oct. 27, 1942 2,299,758

UNITED STATES PATENT OFFICE 2,299,758 SAPOGENIN DERIVATIVE AND PREPARA TION OF THE SAME Russell Earl Marker, State College, Pa., assignor tocorporation Parke, Davis of Michigan & Company, Detroit, Mich., a No Drawing. Application August 3, 1940, Serial No. 351,148 15 Claims. (C. 260-397.2) This invention relates to Sapogenin derivatives and preparation of the same, and more particu These differences are shown below: larly to the preparation of new sapogenin deriva C8 CBIs tives having a reduced side chain. One of the objects of this invention is to pre /N/ Ho /N/N/ pare new Sapogenin derivatives which have a novel structure for the side chain. EIO- A "t B. EIO A B. Another object of this invention is the prepa- - ration of new Sapogenin derivatives having a re Fi duced side chain. O Tigogenin Gitogenin Other objects of this invention Will be apparent CH3 CH from the perusal of this specification and the appended claims. The Steroidal Sapogenins have, in general, the Ho-/N/N/ /N/N/ formula C2H42-4O3-5, of which the portion 5 CaH16O2 is known to be present as a side chain IO-|A || B. HO |A | B attached to ring D of the steroid skeleton. Tschesche and Hagedorn (Ber. 68,2247 (1935)) Y.Y.B Y.Y.OB proposed the formula, Digitogenin Chlorogenin CE CH3. 20 CH3 CHs /N !, C. D kChao.) /N/N/N/ A. B A. B 25 EO- EIO-. A - B N/N/ N/N/ EIO N/N/ Diosgenin SarsaSapogenin H. I have recently suggested (Marker & Rohrmann O - 30 J. Am. Chem. Soc. 61,846 (1939)) that a more CH3 likely structure for the side chain of these CEs. CE8 &H CE steroidal Sapogenins is that shown below. 2 /N / Yoh-off YoH-CH, CE CEb C D 35 O N / / ". /N/N/N/ H 22C C-CE D N M. 16 H-CH, EIO N/ Jh 40 It is apparent that this formulation differs from that of Tschesche and Hagedorn in that the link for the sapogenin, tigogenin, and later Workers age, C27-O-, is transferred from C23 to Ca2. have, with reservations, accepted this formula However, a profound difference in the nature of tion of the steroidal sapogenin side chain. Other the functional character of the side chain oxygen sapogenins such as digitogenin, gitogenin, chloro atoms is implied, for while the Tschesche-Hage genin, diosgenin, and Sarsasapogenin have been dorn formula, is that of an ox,o'-di-tetrahydro shown to differ from tigogenin only in regard to furyl derivative, the Marker-Rohrmann formul the connections between ring A and B, the degree is that of a spiro-ketal. - of saturation of the ring system, and the number Recently it has been found (Marker & Rohr of Substituents attached to these rings, mann, J. Am. Chem. Soc. 61,846, 1516, 2724, 3479, 2 2,299,758 (1939); 62, 647, 896, 1162)) that the side chain present invention may be obtained by the use of of the naturally occurring sapogenins exists in the methods herein to be described and these two modifications. Sarsasapogenin contains one processes and products are claimed without any type of side chain characterized by the fact that implications that the reactions and structures a sapogenin of this type is readily reduced ac 5 involved will ultimately be proved to be as repre cording to the Clemmensen procedure using alco Sented herein. holic hydrochloric acid and amalgamated zinc I have found that steroidal sapogenins having (Marker & Rohrnann, J. Am. Chem. Soc. 61, 846 the regular or coprostane configuration at C5 (i939)) to give tetrahydro derivatives, that is to can be converted by treatment with mineral acid say, new Sapogenin derivatives in which the side and Zinc, under conditions more vigorous than chain has 4 more hydrogen atoms than in the those required merely to reduce a nuclear 3-keto Sapogenins themselves. Tigogenin, gitogenin, group, to form new sapogenin derivatives with digitogenin, chlorogenin and diosgenin behave an altered Side chain. The altered side chain differently from Sarsa Sapogenin in that they are of these new Sapogenin derivatives differs from not reduced by the Clemmensen procedure, that the side chain of the Sapogenins themselves by is to say, they are recovered unchanged after the presence of four more hydrogen atoms. boiling With alcoholic hydrochloric acid and These new reduced Sapogenin derivatives. I call amalgamated zinc. ISOSar'SaSapogenin is Con tetrahydrosapogenins. They show certain char verted under the conditions of the Clemmensen acteristic reactions which distinguish them from reduction to the same tetrahydrosarSasapogenin the Sapogenins themselves. Thus: that Sarsasapogenin itself yields. These facts, and (d) Whereas the Sapogenins are readily halo others which are cited in the references listed, genated in the Side chain, for example, by treat appear to me to be best explained by assuming ment with bromine in acetic acid, the tetrahydro that the two types of steroidal Sapogenin Side Sapogenins show no tendency to halogenate in chains differ in regard to optical isomerism about the side chain under comparable conditions; C22. Accordingly, when it is necessary to dis (b) Whereas the Sapogenins may be hydro tinguish between isomers about C22 I represent genated, under acidic conditions, in the side the two types of side chains by formulae of the chain to give dihydrosapogenins, the tetrahydro following type: Sapogenins show no tendency to add hydrogen CH3 30 to the side chain;

CH8 Cl3 CE O-CE- 2 (c) Whereas the sapogenins are readily oxi dized by selenium dioxide with the formation of /N / Y/ YoH-CH, a red precipitate of metallic selenium (for exam ?cu-erCH-CH2 ple when the Sapogenins are heated for awhile 35 With Selenium dioxide in a mixture of acetic acid rry N/ and benzene), the tetrahydrosapogenins are un affected by treatment with selenium dioxide un Ho-N/N/ der comparable conditions; (d) Whereas in the side chain of the Sarsasapogenin. 40 Sapogenins both of the oxygen atoms appear to ('Sarsasapogenin type' side chain) be insert to the ordinary reagents used to deter CE8 mine the presence of hydroxyl, carboxyl or ketone CE CH3 &H CEI-CBI2- 2 groups, the tetrahydrosapogenins contain in the Side chain. One rather inert oxygen atom and an 45 other OXygen atom present as a hydroxyl group r -K O-CE CH-CH, and apparently this hydroxyl group is a primary hydroxyl group-characterized by its ability to ry N/ be esterified, etherified and replaced by halogen On treatment With reagents customarily used for rolN/N/ this purpose. B The new tetrahydrosapogenin derivatives may, Isosarsasapogenin therefore, be represented by the following formula (“Tigogenin type' side chain) See especially Marker & Rohrmann, J. Am. Ca CH3 Chem. Soc. 62, 896 (1940). Ordinarily where 5 5 N isomerism about C22 is not of importance, the for mula for the sarsasapogenin type of side chain Y- C ID |citinox will be used for configurations both of SarSa Y-M/N/N/ sapogenin and tigogenin type. Y= A B These two types of sapogenin side chains ap (30 pear to be subject to an equilibrium, the Velocity of attainment of which is catalyzed by acidic re N/N/ agents. The equilibrium is influenced by the con Where Y1, Y2 and Ys are substituents attached to figuration of the hydrogen atom at C5, and it methylene carbon atoms in the A-B portion of appears that the following rule holds true. For (i. the Steroid skeleton, said substituents. Y1, Y2 and compounds of the allo series (cholestane type) Ys being members of the class consisting of the tigogenin type of side chain is the more O stable, while for compounds of the regular series k . ( . (coprostane type) at C5 the Sarsa Sapogenin Side H. H. chain is the more stable. For the purpose of greater clarification, the and groups convertible to Marker-Rohrmann formulation of the side chain OH of the steroidal sapongenins will be used in de scribing the invention. It is to be understood, however, that the processes and products of the 5

2,299,758 3 such as by refluxing With ten times its Weight of acetic O-acyl O-alkyi O-aralkyl anhydride for a half hour. The acetic anhydride is removed in vacuo to leave the sirupy diacetate of tetrahydrosarsa Sapogenin. This diacetate re sists crystallization but may be distilled without halogen amino acylamino decomposition. ... The dibenzoate of tetrahydrosarsasapogenin is a characteristic derivative. It may be prepared { {, K. by treating a solution of 100 mg. of terahydro and X is a member of the class consisting of sarsasapogenin in 5 cc. of dry pyridine with 7 -OH and groups hydrolyzable to -OH Such as drops of benzoyl chloride. The mixture is al -O-acyl, --O-aralkyl and halogen. lowed to stand at room temperature for eight The term "methylene carbon atom' refers to a hours and then it is heated on the steam bath carbon atom having not more than two carbon for one hour. Then the solution is poured into atoms attached to it. The methylene carbon water and the resulting mixture extracted with atoms in the A-B portion of the steroid skeleton ether. The ethereal layer is separated, washed are those carbon atoms numbered 1, 2, 3, 4, 6, with dilute hydrochloric acid, dilute sodium car and 7. bonate solution, and finally with water. Then In view of the reactions, already set forth, of the ether is evaporated on the steam bath and these new tetrahydrosapogenin derivatives I have (20. the residue crystallized from aqueous acetone to proposed a tentative structure for compounds of give Small White plates of melting point 149 C. this type (Marker & Rohrmann, J. Am. Chen. This is the dizenzoate of tetrahydrosarsasapo Soc., 61, 846 (1939)). This structure may be il genin. lustrated by the formula, for tetrahydroSarsa Eacample 2 sapogenin which I believe to be as follows: 12 5 To a solution of 1. g. of sarsasapogenin in 200 CE CEs. GH. gh, cc. of 95% alcohol is added 40 g. of amalgamated zinc and the mixture is then heated to boiling. ^ ot-oh-oh-CH-CH-CHot Then 30 cc. of concentrated hydrochloric acid is '30 added slowly to the boiling mixture over a period of four hours. After refluxing the mixture for an additional hour, it is diluted with water, ex tracted with ether and the ethereal extract Ho/N/N/ Washed With sodium carbonate. Solution and With 3 5 water. The ethereal extract is evaporated to H dryness and the residue crystallized from ethyl Tetrahydrosarsasapogenin acetate to give compact white crystals of tetra To prepare my new tetrahydrosapogenin de hydrosarsasapogenin, melting point 193 C. This rivatives I treat steroidal sapogenins, with the is identical with the preparation described in Ex combination of a mineral acid in an organic Sol ample 1, but the yield is even better. went and zinc. I find that for best resultS One Unamalgamated zinc may be substituted for, must make a careful choice of the combination amalgamated zinc in this example, but the yields of mineral acid and organic solvent used. I find obtained are not as satisfactory as those when especially that the use of a homogeneous solu amalgamated zinc is used. Likewise, hydro- , tion is desirable, for if two phases are present i. bromic acid may be substituted for hydrochloric during the reduction the yields are considerably acid, but as a rule this offers no advantage. diminished. For best results I prefer to use amal When the reaction is carried out over a longer gamated zinc and a solution containing from 1 to period of time, crystalline products are more dif 5 parts of concentrated hydrochloric acid per 10 ficult to isolate. This indicates that tetrahydro parts of organic solvent, and as organic solvents SarsaSapogenin is Somewhat sensitive to acids. I prefer to use a lower aliphatic alcohol such as The tetrahydrosarsasapogenin of this example methanol, ethyl alcohol or one of the two isomeric may be sublimed without decomposition at 180° propanols. C. in a high vacuum. followingMy invention examples: may be further illustrated by the Eacample 3 Eacample 1 Satisfactory yields of tetrahydrosarsasapogenin and also of other tetrahydrosapogenins may To a solution of 500 mg. of sarsaSapogenin be obtained by reducing the corresponding side acetate in 100 cc. of 95% alcohol is added 20 g. chain, brominated or side chain chlorinated of amalgamated zinc and the mixture is heated 39 sapogenin. This is illustrated by the preparation to boiling. Then 15 cc. of concentrated hydro of tetrahydrosarsasapogenin from bromosarsa chloric acid is added slowly to the boiling mixture sapogenin. - . . over a period of four hours. At the end of this A solution of 500 mg. of bromosarsasapogenin time the mixture is refluxed for an additional acetate in 100 cc. of 95% alcohol is mixed with hour. Then the solution is poured into water and ti: 20 grams of amalgamated Zinc and the mixture the suspension extracted with ether. The ethe heated to boiling. Then 15 cc. of concentrated real layer is separated, washed with sodium car hydrochloric acid is added slowly over a period bonate solution and with Water and the ether of four hours while keeping the mixture at the : evaporated on the steam bath. The residue is boiling point. The mixture is refluxed an addi crystallized from ethyl acetate to give compact 7) tional hour and then diluted with water. The white crystals, melting point 193 C. This is resulting suspension is extracted with ether, the tetrahydrosarsasapogenin, and it gives a 20 de ethereal extract Washed with sodium" carbonate pression in melting point when mixed with Sarsa solution and with water and the ether removed sapogenin itself. on the steam bath. The residue is crystallized Tetrahydrosarsasapogenin may be acetylated from ethyl acetate to give compact white crystals

4 2,299,758 of tetrahydrosarsasapogenin of melting point to be tetrahydrodesoxysarsasapogenin. For the two substances, M. P. 100-101° C. and M. P. 118 193° C. C., do not depress in M. P. and show the same Eacample 4 carbon, hydrogen analytical figures. Apparently To a solution of 300 mg. of isosarsa Sapogenin they are polymorphous forms, although it is pos (prepared for example as described by Marker sible that they may be stereoisoners. and Rohrmann, J. Am. Chem. Soc., 61, 851 When tetrahydrodesoxySarsaSapogenin is (1939)) in 75 cc. of alcohol is added 15 g. of treated with an etherifying agent, the mono amalgamated zinc. The mixture is brought to a ether of tetrahydrodesoxySarsasapogenin is boil and 12 cc. of concentrated hydrochloric acid formed. Thus, a mixture of 1. g. of tetrahydro is added slowly over a period of four hours. At O desoxySarsasapogenin, 1. g. of triphenylmethyl the end of this time the mixture is diluted. With chloride, and 15 cc. of dry pyridine is allowed to water extracted with ether and the ethereal eX stand at room temperature for five days. Then tract Washed free of acid. The ether is removed the mixture is poured into ice Water, and the on the steam bath and the residue crystallized 5 gummy solid collected. It is recrystallized from from acetone to give compact white crystals of acetone to give the triphenylmethyl ether of tetrahydrosarsasapogenin of melting point 193 tetrahydrodesoxySarsasapogenin as White crys C. This gives no depression in melting point tals. This substance may be represented by the when mixed with an authentic sample prepared formula, by any of the methods given in the earlier ex 20 amples. CB3 CH3 Eacample 5 To a solution of 300 mg. of bronoisoSarsa sapogenin, (prepared, for example, as described by Marker and Rohrmann, J. Am. Chem. Soc., 61, 25 851 (1939) ), in 75 cc. of alcohol is added 12 g. of amalgamated zinc. The mixture is brought to tly a boil and 12 cc. concentrated hydrochloric acid is added over a period of four hours. The mix H ture is refluxed an hour longer and then diluted 30 Eacample 8 with water, extracted with ether, and the ethereal extract worked up as described in previous ex (a) BrOmoSarsa Sapogenin acetate is prepared amples. The residue, after removing the ether, according to the method of Marker and Rohr is crystallized from ethyl acetate to give tetra mann, J. Am. Chem. Soc., 61,846 (1939). 35 (b) To a solution of 500 mg. of bromosarsasa hydrosarsasapogenin of melting point 193 C. pogenin acetate in 100 cc. of methanol is added Eacaniple 6 30 g. of amalgamated zinc. The mixture is (a) DesoxysarsaSapogenin, melting point 214 brought to a boil and 40 cc. of concentrated 215° C. is prepared, for example, as described by hydrochloric acid is added over a period of three Marker and Rohrmann, J. Ann. Chem. Soc., 61, 40 hours. Then the mixture is diluted with water, 1284 (1939). extracted. With ether, and the ethereal layer (b) To a mixture of 150 mg. of desoxySarsa Washed with Water. The ether is removed on sapogenin and 20 g. of amalgamated zinc in 50 the steam bath and the residue is crystallized cc. of boiling 95% alcohol is added 10 cc. of con from ethyl acetate to give tetrahydrosarsasa centrated hydrochloric acid over a period of nine 45 pogenin of melting point 191° C. hours. Then the solution is poured into Water Similar results are obtained when chloro and the mixture extracted with ether. The SarSaSapogenin acetate (prepared by chlorinat ethereal extract is Washed With Water and the ing the Side chain of Sarsasapogenin acetate) is ether evaporated on the steam bath. The sirupy Substituted for bromosarSasapogenin acetate in residue is crystallized from ether-hexane to give 50 this example. silky White needles, melting point 101° C. of tetra The above examples illustrative of this inven hydrodesoxysarsasapogenin. This depresses the tion are Subject to numerous variations which, melting point of dihydrodeSOXySarsa Sapogenin, in View of this disclosure, will be apparent to M. P. 109-110° C. showing that the two substances those skilled in the art. While this invention is 55 limited in its application to steroidal sapogenins are not identical. having the regular or coprostane configuration Instead of using alcohol in this example, other With regard to C5. Within this group numerous organic solvents such as methanol, isopropyl types of compounds may be employed. For ex alcohol, n-propyl alcohol and dioxane may be ample, the Side chain of the steroidal sapogenin used with as satisfactory resultS. may be of either the Sarsasapogenin or of the Eacample 7 60 tigogenin type. Furthermore, the side chain To a solution of 500 mg. of SarsaSapogenone halogenated Sapogenins having either the sarsa in 100 cc. of 95% alcohol is added 50 g. of amal Sapogenin Ortigogenin type of side chain may be gamated zinc. The mixture is brought to a boil employed in the practice of this invention with and 30 cc. of concentrated hydrochioric acid is 65 resultS as Satisfactory as those obtained with added over a period of six hours. At the end the parent unhalogenated Sapogenins. Rings. A of this time, the mixture is diluted With Water, and/or B may bear substituents selected from extracted With ether and the ethereal layer the class consisting of ketonic groups and groups washed with water. After renoval of the ether hydrolyzable to ketonic groups, and hydroxyl the residue is crystallized from ether-hexane to 70 groups and groupS hydrolyzable to hydroxyl give tetrahydrodesoxysarsasapogenin as white groups. Certain transformations of substituents needles of melting point 100°C. Which may be attached to rings A and/or B may The mother liquors from the above crystalliza occur simultaneously with the reduction of the tion of tetrahydrodesoxysarsasapogenin yield a Sapogenin Side chain. For example, nuclear substance, M. P. 118° C., which likewise appears 5 ketone groups at C3 and C6 are reduced in the 2,299,758. 5 course of the reduction to give methylene groups. Sapogenin derivatives which comprises treating Again, ester groups such as an acetoxy group at a compound having the following formula C3 may be Saponified to hydroxyl groups during CE the reduction of the sapogenin side chain. 3 CH: Nuclear halogen groups such as a chlorine atom 5 Ys /N at C3 are usually unaffected during the reduction. 1. }(CH2O) Other modes of isolating and purifying the -- tetrahydrosapogenins of this invention may be Ye /N/N/ N/ used instead of extraction with ether and crys- Y= tallization as indicated in the examples. The 10 3. method Selected for isolation and purification of N/N/ a particular tetrahydrosapogenin, will be deter- H mined by its properties, but in general the methods Will employ customary procedures in where Y1, Y2 and Ys are substituents attached : this art, such as partition between immiscible to methylene carbon atoms in the A-B portion Solvents, high vacuum distillation, chromato of the steroid skeleton, said substituents Yi, Y, graphic adsorption and like, devices. and Y being a member of the class consisting of Accordingly, I do not wish my invention to be limited to any specific embodiment but rather E. desire that it be interpreted as broadly as possible in view of the prior art and the appended claims. 20 What I claim as my invention is: 1. Process for the preparation of steroidal groups hydrolyzable to (=O), Sapogenin derivatives which comprises treating OE a compound of the class consisting of steroidal Sapogenins having the coprostane configuration 25 at C5, the nuclear transformation products E. thereof and side chain halogenated derivatives and groups hydrolyzable to thereof, while in an organic solvent with a min OE eral acid and zinc, under conditions more wig 30 / orous than those required merely to reduce a N nuclear 3-keto group, thereby forming tetra EI hydrosapogenin compounds. 2. Process according to claim 1 in which the and Z is a member of the class consisting of mineral acid is a member of the class consisting hydrogen and halogen, while in an organic sol of hydrochloric acid and hydrobromic acid. 35 vent With a mineral acid and zinc, under condi 3. Process according to claim i wherein the tions more vigorous than those required merely Organic Solvent is a lower aliphatic alcohol. to reduce a nuclear 3-keto group thereby form 4. Process according to claim 1 wherein the ing a tetrahydrosapogenin compound. . zinc has previously been amalgamated. .. 40 14. A tetrahydrosapogenin derivative having 5. Process for the preparation of steroidal the formula, sapogenin derivatives which comprises treating CH3 CE a compound of the class consisting of steroidal Sapogenins having the coprostane configuration Y= at C5, the nuclear transformation products 45 C D |citinox thereof, and side chain halogenated derivatives YH /N/N/N/ thereof, while in a lower aliphatic alcohol Solvent with hydrochloric acid and amalgamated zinc, Y= A B under conditions more vigorous than those re quired merely to reduce a nuclear 3-keto group 50 N/N/ to form tetrahydrosapogenin compounds. Where Y1, Y2 and Ys are substituents attached 6. Process according to claim 1 wherein the to methylene carbon atoms in the A-B portion tetrahydrosapogenin compound is separated from of the steroid skeleton, said substituents Y1, Ye the Solution and isolated. and Ys being members of the class consisting of 7. Process which comprises treating a tetra 55 hydrosapogenin compound with a member of the class consisting of acylating agents, etherifying agents and halogenating agents, thereby obtain K" " ing a sapogenin derivative having in the side H. H. chain thereof a group of the class consisting of 60 and groups convertible to -O-acyl, -O-aralkyl, and halogen. OH 8. Process according to claim 5 wherein the sapogenin treated is one of the class consistin of sarsasapogenin and its esters. - 9. A steroidal Sapogenin derivative of the group X is a member of the class consisting of -OH consisting of tetrahydroSarsaSapogenin and its and groups hydrolyzable to -OH, and the group esters with carboxylic acids, Said compounds C8H190X is a tetrahydrosapogenin side chain at being further characterized by the inertness of tached to ring D of the formula, and obtainable its side chain to the action of bromine in acetic by tetrahydrogenation by means of amalgamated acid and to the action of the Selenium dioxide 70 Zinc and hydrochloric acid of a ring D side chain in acetic acid. identical with that found in a naturally occur 10. TetrahydroSarsaSapogenin. ring Sapogenin, Said tetrahydrogenated side chain 11. Tetrahydrosarsasapogenin diacetate. being further characterized by its inertness to 12. Tetrahydrosarsasapogenin dibenzoate. the action of bromine in acetic acid and to the 13, Process for the preparation of steroidal 75 action of Selenium dioxide in acetic acid,

6 2,299,758 15. A tetrahydrosapogenin derivative having and groups hydrolyzable to the formula, OE CH3 - CE8 5 B X is a member of the class consisting of -OH C D citinox and groups hydrolyzable to -OH, and the group /N/N/N/ CaH17OX is a tetrahydrosapogenin side chain attached to ring D of the formula and obtainable 10 by tetrahydrogenation by means of amalgamated villy Zinc and hydrochloric acid of a ring D side chain N/ identical with that found in a naturally occur where Y is a member of the class consisting of ring Sapogenin, said tetrahydrogenated side chain being further characterized by its inertness to OH l5 the action of bromine in acetic acid and to the action of Selenium dioxide in acetic acid. RUSSELL EARL MARKER.