3-Substituted Iodo Alkenyl Compounds and Methods for Preparing Same

This invention relates to compounds which are eminently useful as intermediates in the preparation of prostaglandins and to methods for preparing such compounds.

The prostaglandins are currently of great interest because of the broad physiologic responses which they elicit in animals, including man. Development of potential application of these compounds has been limited however because of their general unavailability. If they are prepared by total chemical synthesis the processes are long and tedious and the yields of product are low. If they are derived from natural sources difficulties are experienced because of the limitation on the source material from which they are extracted and in obtaining them in significant amounts and inconsistencies are encountered in the activities of the compounds extracted on different occasions.

Process for substantially improving the available supply of prostaglandins, as well as new componds which can function as intermediates in the preparation of known prostaglandins or compounds having prostaglandin-like activity are described in co-pending application Ser. No. 221,058, filed Jan. 26, 1972.

It is the primary purpose of this invention to provide new compounds which find application as key intermediates in the processes of the above-referenced patent application, as well as in other processes, directed to the preparation of known prostaglandins or compounds having prostaglandin-like or anti-prostaglandin-like activity and to methods for preparing such intermediates. The compounds of this invention also exhibit anti-bacterial activity against gram positive bacteria.

The compounds of this invention have the general formula: ##SPC2##

Where

R is hydrogen, methyl or ethyl;

R' is hydrogen, a saturated hydrocarbon chain containing from 1 to about 9 carbon atoms, pentene, hexene, cyclohexyl, or benzyl

X is hydrogen, hydroxy, pyranoxy, OR" where R" is a hydrocarbon chain containing from 1 to about 5 carbon atoms or benzyl, ##EQU3## where R"' is a hydrocarbon chain containing from 1 to about 8 carbon atoms or benzyl, or ##EQU4## where R.sub.1 and R.sub.2 are each a hydrocarbon chain containing from 1 to about 5 carbon atoms, and

n is an integer from 0 to 5.

Among such compounds are included:

3-hydroxy-1-iodo-1-trans-octene

3-hydroxy-1-iodo-1-trans-pentene

3-hydroxy-1-iodo-1-trans-hexene

3-hydroxy-1-iodo-1-trans-4-methyl heptene

3-hydroxy-1-iodo-1-trans-4-ethyl hexene

3-hydroxy-3-methyl-1-iodo-1-trans-octene

3-hydroxy-3-ethyl-1-iodo-1-trans-octene

3-pyranoxy-1-iodo-1-trans-octene

3-(.alpha.-ethoxy)-ethoxy-1-iodo-1-trans-octene

3-benzyloxy-1-iodo-1-trans-octene

3-acetyloxy-1-iodo-1-trans-octene

3-hydroxy-1-iodo-1-trans-heptene

3-hydroxy-1-iodo-1-trans-1,6-octadiene

3-hydroxy-1-iodo-1-trans-1,6-nonadiene

3-hydroxy-1-iodo-4-cyclohexyl-1-trans-butene

3-hydroxy-1-iodo-5-cyclohexyl-1-trans-pentene

3-hydroxy-1-iodo-6-cyclohexyl-1-trans-hexene

3-hydroxy-1-iodo-7-cyclohexyl-1-trans-heptene

3-hydroxy-1-iodo-8-cyclohexyl-1-trans-octene

3-hydroxy-1-iodo-4-benzyl-1-trans-butene

3-hydroxy-1-iodo-5-benzyl-1-trans-pentene

3-hydroxy-1-iodo-6-benzyl-1-trans-hexene

3-hydroxy-1-iodo-7-benzyl-1-trans-heptene

3-hydroxy-1-iodo-8-benzyl-1-trans-octene

1-iodo-4-cyclohexyl-1-trans-butene

1-iodo-5-cyclohexyl-1-trans-pentene

1-iodo-6-cyclohexyl-1-trans-hexene

1-iodo-7-cyclohexyl-1-trans-heptene

1-iodo-8-cyclohexyl-1-trans-octene

1-iodo-4-benzyl-1-trans-butene

1-iodo-5-benzyl-1-trans-pentene

1-iodo-6-benzyl-1-trans-hexene

1-iodo-7-benzyl-1-trans-heptene

1-iodo-8-benzyl-1-trans-octane

These compounds can be prepared in accordance with the procedure set forth in the following example which, by way of illustrating the process, relates specifically to the preparation of 3-hydroxy-1-iodo-1-trans-octene .

2 Molar equivalents of diisobutylaluminum hydride was added to 1 molar equivalent of 1-octyn-3-ol in dry heptane (40 ml/100 m moles of 1-octyn-3-ol) while maintaining the temperature below 40.degree. C. When the exothermic reaction had subsided, the reaction mixture was heated at about 50.degree. C. for 2.5 hours. The heptane was then removed under reduced pressure (0.2 mm Hg) and the residue obtained was diluted with dry tetrahydrofuran (40 ml/100 m moles of diisobutylaluminum hydride). To this solution, cooled to -50.degree. C., was slowly added a solution of 2 molar equivalents of iodine in dry tetrahydrofuran (40 ml/100 m moles of iodine) while maintaining the temperature at about -50.degree. C. The iodine colour disappeared at the beginning and a gas (probably hydrogen) was given off. After about 1 molar equivalent of iodine was added, the gas evolution ceased and the iodine colour disappeared more slowly, the solution taking on a red colour. After all the iodine had been added, the reaction mixture was allowed to warm up to room temperature, whereupon the diisobutylalane formed in the reaction was decomposed at 20.degree.-30.degree. C. by the dropwise addition of 20% sulfuric acid. When the isobutane evolution had diminished, the reaction mixture was poured into ice - 20% sulfuric acid. The reaction mixture was extracted four times with pentane and the combined organic extract was washed successively with sodium thiosulfate, saturated sodium bicarbonate and saturated sodium chloride solutions, and dried over magnesium sulfate. Evaporation of the dried extract gave a yellow oil. The nmr spectrum (CDCl.sub.3) of the product after all volatile material had been distilled off, showed that some of the saturated iodide, 3-hydroxy-1-iodo-octane was present.

The product was further treated to remove any 3-hydroxy-1-iodo-octane and possible diiodo-3-hydroxyoctane present. To accomplish this the reaction product was mixed with an excess (3-5 times) of triethylamine and the mixture heated at about 94.degree. C. for 20 hours. The excess triethylamine was evaporated off and water was added to the residue. The mixture was shaken for some time. Most of the black oily residue dissolved in the water and the total mixture was extracted 5 times with pentane. The combined pentane extract was washed successively with dilute hydrochloric acid, saturated sodium bicarbonate, sodium thiosulfate, saturated sodium bicarbonate and saturated sodium chloride solutions and dried over magnesium sulfate. The product obtained after evaporation of the pentane was chromatographed on silica gel and elution with benzene produced pure 3-hydroxy-1-iodo-1-trans-octene, wt: 12.5 g. (24.6%).

As an alternative to the procedure of Example 1 above, the hydroalumination can be carried out by complexing the hydroxy function in 1-octyn-3-ol with trisobutylaluminum to give an aluminum alkoxide and isobutane gas, one molar equivalent of diisobutylaluminum hydride then being added to form the vinylalane. This procedure, which is set out with greater specificity in Example 2 below, offers certain advantages over the procedure of Example 1, above, in that the quantity of undesired 1-iodo-3-hydroxyoctane and diiodo-3-hydroxyoctane formed in the reaction mixture is reduced and the desired product, 3-hydroxy-1-iodo-1-trans-octene, can be obtained in higher yields by vacuum distillation.

To 1.26 g. (0.01 moles) of 1-octyn-3-ol in 8 ml. in dry heptane was added dropwise 6.18 ml. (0.03 moles) of triisobutylaluminum at 10.degree.-15.degree. C.; 1.82 ml. (0.01 moles) of diisobutylaluminum hydride was then added and the reaction mixture was heated at 50.degree.-55.degree. C. for 2 hours. The solution was then cooled and the heptane removed under reduced pressure. The residue obtained was diluted with 12 ml. of dry tetrahydrofuran. After cooling the solution to -50.degree. C., 10.26 g. (0.04 moles) of iodine in 16 ml. of dry tetrahydrofuran was added dropwise. The dark solution was warmed to room temperature and the alane was decomposed at 20.degree.-30.degree. C. with 20% H.sub.2 SO.sub.4. After the isobutane evolution had diminished, the reaction mixture was poured into ice and extracted four times with pentane. The pentane extract was washed successively with saturated NaHCO.sub.3, sodium thiosulfate, saturated NaHCO.sub.3 and saturated NaCl solutions. After drying the pentane over MgSO.sub.4, it was evaporated to give a dark oil. To remove the iodo-3-hydroxyoctane, the mixture was heated for 16 hours at 90.degree. C. with 0.005 moles of triethylamine. The excess triethylamine was evaporated off and water was added to the residue. Most of the dark oily residue dissolved in the aqueous layer and the total mixture was extracted with pentane. The pentane extract was washed with dilute hydrochloric acid, saturated sodium bicarbonate and saturated sodium chloride solutions and dried over magnesium sulfate. After evaporation of the pentane, the residue was distilled in vacuo to yield pure 3-hydroxy-1-iodo-1-trans-octene (40-50% molar basis). Some 1-octyn-3-ol was recovered.

The hydroalumination methods of the foregoing Examples are readily applicable to compounds having the formula ##SPC3##

where

R is hydrogen, methyl or ethyl;

R' is hydrogen, a saturated hydrocarbon chain containing from 1 to about 9 carbon atoms, pentene, hexene, cyclohexyl, or benzyl

X is hydrogen, pyranoxy, OR" where R" is a hydrocarbon chain containing from 1 to about 5 carbon atoms or benzyl, ##EQU5## where R'" is a hydrocarbon chain containing from 1 to about 8 carbon atoms or benxyl, or ##EQU6## where R.sub.1 and R.sub.2 are each a hydrocarbon chain containing from 1 to about 5 carbon atoms, and

n is an integer from 0 to 5

to produce the iodo compounds hereinbefore set forth.

Of the compounds which respond to the above formula 1-octyn-3-ol is a preferred reactant. Other of the compounds responding to the said formula which find ready application include those in which X is an ether configuration which is susceptible to hydrolysis by mild acid, including cyclic ether, or where X is an ester configuration (for example 3-acyloxy-1-octyne compounds such as 3-acetoxy-1-octyne).

The aluminum complexing agent in each case will be chosen to provide the greatest possible yield of desired product. For example, it has been found that when 3-tetra-pyranoxy-1-octyne, 3-(.alpha.-ethoxy)-ethoxy-octyne or 3-acetoxy-1-octyne are the compounds of choice for hydroalumination, the process described in Example 1 provides a better yield of the desired compound, 3-hydroxy-1-iodo-1 -trans-octene, than does the procedure of Example 2. However, as is pointed out more specifically below, when diisobutylaluminum is used as the hydroalumination agent, it is essential to use that agent in the ratio of two molar equivalents to one molar equivalent of the particular compound which is being complexed. On the other hand, when triisobutylaluminum is used, as in the process of Example 2, such agent can be used in a molar equivalent ratio to the compound being complexed of 1:1 or greater.

It is also to be understood that the saturated hydrocarbon chain represented by R' in the foregoing general formulae does not have to be a straight chain configuration but can be branched. For example, 4-, 5-, or 6-, methyl heptyne or other branched chain configurations can be readily substituted for the hydrocarbon chain in the 1-octyn-3-ol reactant.

The hydroalumination process as described in Example 1 above, and where diisobutylaluminum is used as the hydroalumination agent, is similar to the general procedure described by G. Zweifel et al, J. Amer. Chem. Soc. 89, 2753 (1967). There are, however, some major, and critical, differences. With the 3- position substituted, compounds which must be used as the starting materials to produce the novel compounds of this invention, the Zweifel et al process is inoperative. It is only when two molar equivalents of the hydroalumination agent, diisobutyaluminum hydride, are used that the hydroalumination proceeds to produce the desired compounds. In addition, the treatment with triethylamine or, other basic trialkylamines, such as, for example, trimethylamine is essential to the elimination of undesirable by-products from the reaction mixture and to the production of the desired compound in essentially pure form.

The processes of this invention permit the ready recovery of the products thereof in the trans isomeric configuration, the preferable isomer for the preparation of physiologically-active prostaglandins or compounds having prostaglandin-like activity.

The iodo compounds of this invention are readily converted into the corresponding lithium compounds in accordance with the procedure described in the following Example which is directed, by way of illustration, to the preparation of 1-lithium-1-trans-octene.

In a three-necked round bottom flask equipped with a mechanical stirrer (wire blade) and pressure equalizing dropping funnel was placed 4-6 molar equivalents of fine lithium powder and dry diethyl ether (2 ml/1 mmole of vinyl iodide) freshly distilled over lithium aluminum hydride. A blanket of argon was maintained at all times. To this rapidly stirred mixture, which was cooled in an ice-bath, was added 1 molar equivalent of 3-hydroxy-1-iodo-1-trans-octene (vinyl iodide) in dry diethylether (2 ml/1 mmole of vinyl iodide). After a few drops of the vinyl iodide in ether was added, a Gilman test was performed. If the test was positive, the addition of the vinyl iodide was continued. If the test was negative, the addition of the vinyl iodide was stopped and the rapid stirring of the lithium solution continued. The Gilman test was performed at various intervals. When a positive test was obtained, the addition of the vinyl iodide was recommenced. The vinyl iodide solution was added over 2 hours. The solution was stirred with ice-bath cooling for a further 4 hours. The solution of the vinyl lithium was transferred to a storage bottle under argon through a glass wool filter to filter out any unreacted lithium.

The 1-lithium-1-trans-octene was utilized in preparing prostaglandins in accordance with the procedures shown in the aformentioned co-pending application and the following Example.

A solution of tri-n-butylphosphine-copper (I) iodide complex (1.6127 g.) in 21 ml. of dry diethyl ether was treated with 34 ml. of 0.242 M solution of 1-lithium-1-trans-octene in ether at -78.degree. C. Under a blanket of nitrogen. After stirring at -78.degree. C. for 30 minutes, 1.33 g. of 2-(6'carboethoxyhexyl)-2-cyclopentene-4-tetrahydropyranoxy-1-one (method of preparation shown in "Total Synthesis of (+)-15-Deoxyprostaglandin E.sub.1 ", Charles J. Sih et al, Chem. Comm. No. 4, p. 240 (1972)) in 25 ml. of dry diethyl ether was added dropwise to the yellow vinyl copper solution. The solution was allowed to warm to 0.degree. C. (ice-bath) and stirred at this temperature for 1.5-1.2 hours. The reaction mixture was allowed to warm to room temperature and 28 ml. of a 20% aqueous ammonium chloride solution, pH 8.3, was added to complex the copper. The ethereal layer was separated from the blue aqueous layer, which was extracted 3 times with ether. The combined ether extracts were washed twice with a saturated sodium chloride solution and dried over magnesium sulfate. Evaporation of the ethereal extract afforded a reddish yellow oil. This oil was dissolved in 10 ml. of acetic acid-water (65:35) and tetrahydrofuran in the ratio of 1 to 0.1 ml. and was stirred at 30.degree. C. overnight according to the procedure of E. J. Corey, T. K. Schaaf, W. Huber, U. Koelliber and N. Weinshenker, J. Amer. Chem. Soc., 92, 397 (1970). The solvent was removed and the oil product was chromatographed over a silicic acid-Celite (85:15) column (3/4 .times. 4 inches). The column was eluted with a gradient system consisting of 400 ml. of benzene-ethyl acetate (75:25) in the reservoir. 7 ml. fractions were collected. Fractions 33-48 afforded 155 mg. of ultraviolet positive material which had the following characteristics: nmr (COCl.sub. 3) .delta.1.21 (t, 3, J = HZ, CH.sub.3), .delta.3.23(m, 1, H at C-12), .delta.4.13 (q 2, J = 6,7 HZ, CH.sub.3 CH.sub.2), .delta.5.62 (m, 2, vinyl H at C-13 and C-14), .delta.6.17 (m, 1, H at C-10), .delta.7.49 (m, 1, H, at c-11); m/e at 348;.lambda..sub.max.sup.alc 217 nm (10,000) and was identified thereby as dl 15 deoxo PGA.sub.1 ethyl ester.

Fractions 65-100 were pooled and evaporated to dryness to yield 717 mg. of a material having the following characteristics: nmr (CCl.sub.4, 100 m HZ) .delta.1.21 (t, 3, J = 6.7 HZ, CH.sub.3), .delta.4.13 (q, 2, J = 6.7 HZ, CH.sub.3 CH.sub.2), .delta.4.20 (m, 1, H--C--OH), .delta.5.28 (d of d, J.sub.12,13 = 7 HZ, J.sub.13,14 = 16 HZ - C.sub.13.apprxeq.), 5.58 (d of t, J.sub.13,14 - 16 HZ, J.sub.14,15 = 6 HZ, .apprxeq. C.sub.14 H--); ir (Nujol) 962 cm.sup..sup.-1 (trans CH=CH); molecular ion a m/e 366.28145 (theory for C.sub.22 H.sub.38 O.sub.4, 366.27699) and which was determined to be dl-15-deoxoprostaglandin E.sub.1 ethyl ester.

This ester can be readily converted to dl-15-deoxo PGE.sub.1 by methods which are well known in the art, such as, for example, by exposing it to the action of an esterase-producing microorganism. (Sih et al., Chem. Comm. supra.)

Pharmacological assays were conducted with dl-15-deoxoprostaglandin E.sub.1 using the guniea pig tracheal strip (smooth muscle) methods described by J. W. Constantine, Journal Pharmacy & Pharmacology 17, 3184 (1955) and R. Patterson, Journ. Allergy 29, 165 (1958). dl-15-deoxoprostaglandin E.sub.1 exhibited an ED.sub.50 concentration (effective dose giving 50% of maximum response) on separate determinations of 1.4 .times. 10.sup..sup.-6 M and 1.06.sup..sup.-6 M indicating its pharmacological applicability in place of natural prostaglandins where smooth muscle controlling or responsive effects are being sought.

In addition to having utility as key intermediates in the total chemical synthesis of prostaglandins as described hereinbefore and in co-pending application Ser. No. 221,058, filed Jan. 26, 1972, the compounds of this invention are characterized by activity against gram positive bacteria as is shown in Example 5 below.

To 10 ml. of Penicillin assay seed agar (J-1095-C, Fisher Scientific Co.) per petri-dish was added 0.1 ml. of a 24 hour culture of the test organisms in nutrient broth. The test compounds 3-hydroxy-1-iodo-1-trans-octene (HVI) and 1-iodo-1-trans-octene (VI) was dissolved in method to give a concentration of 1.9 .times. 10.sup..sup.-2 M. 1/10 milliliter of the test compounds was added to a filter paper disk (12.7 mm.), which was layered on top of the agar plate. The petri-plate was incubated at 25.degree. C. for 48 hours, and the zone of inhibition was measured.

It is evident from the above that the 3-carbon-substituted compounds of this invention exhibit substantial antibacterial activity against gram positive organisms as compared with similar compounds not having a substituent at that position in the hydrocarbon chain.