RENIN INHIBITORY PEPTIDES

Abstract: Renin inhibitory peptides of the formula: wherein A is, e.g., hydrogen; B is, e.g., absent or glycyl; D is absent or where Z is (CH₂) n and n is 1 or 2: or -S-; R¹ is, e.g., hydrogen; R² is, e.g., hydrogen; R³ is, e.g., C₃₋₆ alkyl; R⁴ is, e.g., hydrogen; R⁵ is, e.g., hydrogen; E is OR, NHR, or N)R)₂, where each R may be the same or different and is hydrogen or C₁₋₄ alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration: and a pharmaceutically acceptable salt thereof. Those peptides are useful for treating various forms of renin-associated hypertension and hyperaldosteronism. Pharmaceutical compositions containing those peptides are also disclosed.

Description: TITLE OF THE INVENTION RENIN INHIBITORY PEPTIDES BACKGROUND OF THE INVENTION 1. Field of The Invention The present invention is concerned with novel peptides which inhibit renin. The present invention is also concerned with pharmaceutical compositions containing the novel peptides of the present invention as active ingredients, with methods of treating renin-associated hypertension and hyperaldosteronism, with diagnostic methods which utilize the novel peptides of the present invention, and with methods of preparing the novel peptides of the present invention. Renin is a proteolytic enzyme of molecular weight about 40,000, produced and secreted by the kidney. It is secreted by the juxtaglomerular cells and acts on the plasma substrate, angiotensinogen, to split off the decapeptide angiotensin I, which is converted to the potent pressor agent angiotensin II. Thus, the renin-angiotensin system plays an important role in normal cardiovascular homeostasis and in some forms of hypertension. In the past, attempts to modulate or manipulate the renin-angiotensin system have met with success in the use of inhibitors of angiotensin I converting enzyme. In view of this success, it seems reasonable to conclude that a specific inhibitor of the limiting enzymatic step that ultimately regulates angiotensin II production, the action of renin on its substrate, would be at least equally successful. Thus, an effective inhibitor of renin has been long sought as both a therapeutic agent and as an investigative tool. 2. Brief Description of the Prior Art There has been substantial interest in the synthesis of useful renin inhibitors for many decades; and the following table lists the major classes of renin inhibitors that have been studied, as well as their inhibition constants (K.): Class K. (M) Renin antibody probably 10 Pepstatin lo¯6 - Phospholipids 10-3 Substrate analogs Tetrapeptides 10 Octa- to tridecapeptides 10-5 - 10¯6 Umezawa et al., in J. Antibiot. (Tokyo) 23: 259-262, 1970, reported the isolation of a peptide from actinomyces that was an inhibitor of aspartyl proteases such as pepsin, cathepsin D, and renin. This peptide, known as pepstatin, was found by Gross et al., Science 175:656, led71, to reduce blood pressure. in vivo after the injection of hog renin into nephrectomized rats. However, pepstatin has not found wide application as an experimental agent because of its limited solubility and its inhibition of a variety of other acid proteases in addition to renin. The structure of pepstatin is shown below: EMI3.1 To date, many efforts have been made to prepare a specific renin inhibitor based on substrate analogy. Since the human renin substrate has only recently been elucidated (Tewksbury et al., Circulation 59, 60,- Supp. II: 132, Oct. 1979) , heretofore substrate analogy has been based on the known pig renin substrate. While the human and pig renin substrates are not the same, the substrate analogy based on pig renin has always been considered acceptable in the art as predictive of human renin inhibitory activity because of the closely related activity of the two renins. Thus, while pig renin does not cleave the human renin substrate, human renin, on the other hand, dqes cleave the pig renin substrate. See Poulsen et al., Biochim. Biophys. Acta 452:533-537, 1976; and Skeggs, Jr. et al., J. Exp. Med. 106:439-453, 1957. It has been found, for example, using pig renin substrate analogy, that the octapeptide sequence extending from histidine-6 through tyrosine-13 has kinetic parameters essentially the same as those of the full tetradecapeptide renin substrate. The amino acid sequence of the octapeptide in pig renin substrate is as follows: 6 7 8 9 10 11 12 13 -His-Pro-Phe-His-Leu-Leu-Val-Tyr- Renin cleaves this substrate between Leu10 and Leu11. The renin inhibitory peptides of the present invention are also based on human renin substrate analogy. The human renin octapeptide sequence, related to the pig renin substrate octapeptide, is as follows: 6. 7 8 9 10 11 12 13 -His-Pro-Phe-His-Leu-Val-Ile-His- Similar to the pig renin substrate, human renin cleaves this substrate between Leu10 and Val11. Kokubu et al., Biochem. Pharmacol. 22: 3217-3223, 1973, synthesized a number of analogs of the tetrapeptide found between residues 10 to 13 of the pig renin substrate, but while inhibition could be shown, inhibitory constants were only of the order of 10-3M Analogs of a larger segment of renin substrate were also synthesized: Burton et al., Biochemistry 14: 3892-3898, 1975, and Poulsen et al., Biochemistry 12: 3877-3882, 1973. Two of the major obstacles which had to be overcome to obtain an effective renin inhibitor useful in vivo were lack of solubility and weak binding (large inhibitory constant). Modifications to increase solubility soon established that the inhibitory properties of the peptides are markedly dependent on the hydrophobicity of various amino acid residues, and that increasing solubility by replacing lipophilic amino acids with hydrophilic isosteric residues becomes counterproductive. Other approaches to increasing solubility have had limited success. Various modifications designed to increase binding to renin have also been made, but here too, with only limited success. For a more detailed description of past efforts to prepare an effective inhibitor of renin1 see Haber and Burton, Fed. Proc. Fed. Am. Soc. Exp. Biol. 38: 2.768-2773, 1979. For other articles describing previous efforts to devise renin inhibitors, see Marshall, Federation Proc. 35: 2494-2501, 1976; Burton et al., Proc. Natl. Acad. Sci. USA 77: 5476-5479, Sept. 1980; Suketa et al., Biohemistry 14: 3188, 1975; Swales, Pharmac. Ther. 7: 173-201, 1979; Kokubu et al., Nature 217: 456-457, Feb. 3, 1968; Matsushita et al., J. Antibiotics 28: 1016-1018, Dec. 1975; Lazar et al., Biochem. Pharma. 23: 2776-2778, 1974; Miller et al., Biohem. Pharma. 21: 2941-2944, 1972; Haber, Clinical Science 59:7s-19s, 1980; and Rich et al., J. Org. Chem. 43: 3624, 1978, and J. Med. Chem. 23: 27, 1980. DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS In accordance with the present invention there are provided renin inhibitory peptides of the formula: EMI6.1 wherein: A is EMI6.2 EMI6.3 where n is 0 to 5 and R" has the same meaning as set out further below, and may additionally be hydrogen; B is absent; glycyl; sarcosyl; or EMI6.4 D is absent; or EMI6.5 where Z is (CH2)n and n is 1 or 2; or -S-; R1 is hydrogen; C14 alkyl; hydroxy t:1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hyaroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C24 alkyl; guanidyl C2¯3 alkyl; or methylthiomethyl; R is hydrogen; C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3 is C36 alkyl; C37 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; R4 is hydrogen; EMI7.1 where R6 is hydrogen; C1-4 alkyl; hydroxy; or C3-7 7 cycloalkyl; R5 is hydrogen; EMI7.2 where R is hydrogen, C14 alkyl, hydroxy, or C3-7 cycloalkyl; or -CH2-R7, where R is 4-imidazolyl, amino C24 alkyl, 2-, 3- or 4-pyridyl or guanidyl C23 alkyl; and E is OR8; NHR8, or N(R8) 2' where each R8 may be the same or different and is hydrogen or C1-4 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. In the above definitions, the term "alyl is intended to include both branched and straight chain hydrocarbon g-roups having the indicated number of carbon atoms. The novel renin inhibitory peptides of the present invention may also be described in terms of common amino acid components and closely related analogs thereof, in accordance with the following formula: A-B-B-D-F-G-Sta-H-I-B-E (if.) The A,B,D, and E components correspond to the same portions of Formula I. In Formula II, Sta represents the unusual amino acid statine and its closely related analogs, and its presence constitutes a unique feature of the renin inhibitory peptides of the present invention. Statine may be named as 4(S)-amino-3(S)-hydroxy- 6-methylheptanoic acid, and may be represented by the following formula: EMI8.1 As shown in Formula III above, the delta-substituent in naturally-occurring statine is isopropyl, or a leucine sidechain, essentially. As shown in Formula I by the R3 substituents, the isopropyl group may be replaced by higher alkyl groups up to six carbon atoms, cycloalkyl groups containing from three to seven carbon atoms, phenyl, and phenyl mono substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo. The phenyl substituent is especially preferred. These modifications of the naturally-occurring statine structure are in accordance with the hydrophobicity considered necessary to maintain the inhibitory activity of the total peptide. The remaining common amino acid components of Formula II are as follows: A has the same meaning as above in Formula I; B is absent, Gly, Ala, Val, Leu, Ile, Phe, Tyr, Trp, His, Lys, Orn, Arg, or Met; D is absent or Pro; F is Ala, Leu, Phe, Tyr, or Trp; G is Ala, Leu, Phe, Tyr, Trp, His, Lys, Orn, Arg, or Met; H is the same as F and may additionally be Ser, Gly, Val, Ile, or Thr; I is the same as H and may additionally be His, Arg, Lys, or Orn; and E has the same meaning as above in Formula I. It will be understood that closely related analogs of the above common amino acids, for example, aliphatic amino acids- in addition to Ala, Val, Leu, and Ile, such as a-aminobutyric acid (Abu), and substituted phenyl derivatives of Phe, are included in the broad description of the novel inhibitory peptides of the present invention represented by Formula I and its definitions. Thus, the peptides of Formula II and its definitions, including the derivatives of naturally-occurring statine represented by the definitions of the R3 substituent in Formula I, represent preferred peptides of the present invention. Especially preferred inhibitory peptides of the present invention are the following: iso-Butyryl-His-Pro-Phe-His-Sta-Val-His-Gly-NH2 iso-Butyryl-His-Pro-Phe-His-Sta-Ile-His-NH2 tert-Butyloxycarbonyl-Phe-His-Sta-Ile-His-NH2 Benzyloxyzarbonyl-Phe-His-Sta-Ile-His-NH2 iso-Valeryl-His-Pro-Phe-His-Sta-Ile-His-NH2 iso-Valeryl-His-Pro-Phe-His-S ta-Leu-His -NH2 His-Pro-Phe-His-S ta-Leu-Phe-NH2 iso-Valeryl-His-Pro-Phe-His-Sta-Leu-Phe-NH2 Acetyl-Pro-Phe-His-Sta-Leu-phe-NH2 Acetyl-Phe-His-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl-Phe-His-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl-His-Pro-Phe-Phe-Sta-Leu-Phe-NH2 iso-Butyryl-His-Pro-Phe-His-Sta-Ala-Phe-NH2 iso-Butyryl-His-Pro-Phe-His-Sta EMI10.1 <tb> Cyclo <tb> #hexyl-Phe <SEP> <tb> Ala <tb> -NH2 <RTI ID=10.6> tert-Butyloxycarbonyl-His-Pro-Phe-His-Sta-Leu-Leu-OCH3 tert-Butyloxycarbonyl-His-Pro-Phe-His-Sta-Leu-Tyr-NH2 iso-Butyryl-His-Pro-Phe-His-Sta-Leu-Phe-Lys-NH2 tert-Butyloxycarbonyl-t1is-Pro-Phe-±- I-Phe-Sta-eu-Phe-N2 iso-Valeryl-His-Pro-Phe-His-S ta-Leu-Val-Phe-NH2 The inhibitory peptides of the present invention may be better appreciated in terms of substrate analogy from the following illustration of Formula I alongside the octapeptide sequence of a portion of the pig renin substrate, which renin cleaves between LeulO and Leu11: : His-Pro Phe His Leu Leu Val Tyr (5) 6 7 8 9 10(11) 12 13 (14) EMI11.1 Statine (IV.) As can be seen, a unique aspect and essential feature of the present invention is the substitution of the single statine amino acid component for the double amino acid sequence: Leu10-Leu11 in the endogenous pig renin substrate. It is believed that substitution of statine for both leucine amino acids rather than just one leucine results in an improved substrate analogy due to the greater linear extent of statine as compared to a single leucine component. Thus, statine more closely approximates Leu-Leu in linear extent, and thereby provides a better "fit" to the renin enzyme. The inhibitory peptides of the present invention may also- be better appreciated in terms of substrate analogy from the following illustration of Formula I alongside the octapeptide sequence of a portion of the human renin substrate, which renin cleaves between Leu10 and Valll: His - Pro - Phe His Leu Val Ile His (5) 6 7 8 9 10 (11) 12 13 (14) EMI12.1 Statine (V.) As can be seen, a unique aspect and essential feature of the present invention is the substitution of the single statine amino acid component for the double amino acid sequence: Leul0-Valll in the endogenous human renin substrate. It is believed that substitution of statine for both the leucine and valine amino acids rather than just the leucine results in an improved substrate analogy due to the greater linear extent of statine as compared to a single leucine component. Thus, statine more closely approximates Leu-Val in linear extent, and thereby provides a better "fit to the human renin enzyme. In the endogenous substrate it is also preferred to substitute Leu for Val12 and Phe for Tyr13 in order to enhance the inhibitory activity of the resulting peptide. Thus, a most preferred inhibitory peptide of the present invention is His-Pro-Phe-His-Sta-Leu-Phe-NH2. Other specific preferred peptides of the present invention are the following, set out in order by variations in the structure at different positions in the overall peptide sequence, represented by the numbered positions in Formulas IV and V: Variations in position (5): 10 (5) 6 7 8. 9 (11) 12 13 (14) Hydrogen - His -Pro-Phe-His-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl- " " " " " " " " " iso-Valeryl- N n N n n iso-Butyryl- n n n tert-Butyloxycarbonyl Pro- N n N Variations in position (6): 10 (5) 6 7 8 9 (11) 12 13 (14) Hydrogen - X*-Pro-he-His-Sta-Leu-Phe-NH2 " Sar- " " " " " " " " D-His- " " " " " " Acetyl- X- " " " " " " " tert-Butyloxycarbonyl- " " " N Phenoxyacetyl- " " " " " " " " Variations in position (7): 10 (5) 6 7 8 9 (11) 12 13 (14) Hydrogen - X - X-Phe-His-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl- " " " " " " " " Cyclopentylcarbonyl- N N n n n n n Acetyl- " " " " " " " " -D- iso-Valeryl- His-Pro- " " " " " " Variations in position (8): 10 (5) 6 7 8 9 (11) 12 13 (14) iso-Butyryl- Bis-Pro-Ala-Phe-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl- " N Phe-His- " " " "N *X=amino acid absent from position. Variations in position (9): 10 (5) 6 7 8 9 (11) 12 13 (14) iso-Butyryl- His-Pro-Phe-Ala-Sta-Leu-Phe-NH2 tert-Butyloxycarbonyl- " " " -Phe- " " " " -p-I- " " " Phe- " " " " Variations in position (12): 10 (5) 6 7 8 9 (11) 12 13 (14) iso-Butyryl- His-Pro-Phe-His-Sta-Gly-Phe-NH2 N N " n N " -Ala- " n n " n " N -Val- " " N " N n " N -Ile- " " n n n n n n -Phe- N " -Cyclohexyl N n n n N " Ala- " " Variations in position 13: 10 (5) 6 7 8 9 (11) 12 13 (14) iso-Butyryl- His-Pro-Phe-His-Sta-Leu-Leu-OCH3 N n N n n " -Tyr-NH2 tert-Butyloxycarbonyl- X X " " " -Trp-NH2 N " " " n " " -Ala-OCH3 iso-Valeryl- N " n " " " -Val-Phe-NH2 Variations in position 14: 10 (5) 6 7 8 9 (11) 12 13 (14) iso-Valeryl- His-Pro-Phe-His-Sta-Leu-Phe-OH N N " " " " " " iso-Butyryl- N N n n N N N -Gly-OH N N " " " " " " N " " " " " " Leu-Phe-NH2 " " " " " " " Leu-Lys-NH2 The Formula I compounds can be used in the form of salts derived from inorganic or organic acids and bases Included among such acid addition salts are the following: acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptanoate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, 2-hydroxyethanesulfonate r lactate, maleate, methane- sulfonate, 2-naphthalenesulfonate, nicotinate, oxalate, pamoate, pectinate, persulfate, 3-phenylpropionate, picrate, pivalate, propionate, succinate, tartrate, thiocyanate, tosylate, and undecanoate. Base salts include ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N-methyl-D-glucamine, and salts with amino acids such as arginine, lysine, and so forth. Also, the basic nitrogen-containing groups- can be quaternized with such agents as lower alkyl halides, such as methyl, ethyl, propyl, and butyl chloride, bromides and iodides; dialkyl sulfates like dimethyl, diethyl, dibutyl; and diamyl sulfates, long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and iodides, aralkyl halides like benzyl and phenethyl bromides and others. Water or oil-soluble or dispersible products are thereby obtained The novel peptides of the present invention possess an excellent degree of activity in treating renin-associated hypertension and hyperaldosteronism. For these purposes the compounds of the present invention may be administered parenterally, by inhalation spray, or rectally in dosage unit formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. In addition to the treatment of warm-blooded animals such as mice, rats, horses, dogs, cats, etc., the compounds of the invention are effective in the treatment of humans. The pharmaceutical compositions may be in the form of a sterile injectable preparation, for example as a sterile injectable aqueous or oleagenous suspension. This suspension may be formulated according to the known art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally-acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectibles. The peptides of this invention may also be administered in the form of suppositories for rectal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient which is solid at ordinary temperatures but liquid at the rectal temperature and will therefore melt in the rectum to release the drug. Such materials are cocoa butter and polyethylene glycols. Dosage levels of the order of 2 to 35 grams per day are useful in the treatment of the above indicated conditions. For example renin-associated hypertension and hyperaldosteronism are effectively treated by the administration of from 30 milligrams to 0.5 grams of the compound per kilogram of body weight per day The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the host treated and the particular mode of administration. It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination and the severity of the particular disease undergoing therapy. Thus, in accordance with the present invention there is further provided a pharmaceutical composition for treating renin-associated hypertension and hyperaldosteronism, comprising a pharmaceutical carrier and a therapeutically effective amount of a peptide of the formula: EMI19.1 wherein A, B, D, R1, R2, R3 R4 R5, and E have the same meaning as recited further above for Formula I; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. Also, in accordance with the present invention there is still further provided a method of treating renin-associated hypertension and hyperaldosteronism, comprising administering to a patient in need of such treatment, a therapeutically effective amount of a peptide of the formula: EMI19.2 wherein A, B, D, R1, R2, R3, R4, R5, and E have the same meaning as recited further above for Formula I; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. The renin inhibitory novel peptides of the present invention may also be utilized in diagnostic methods for the purpose of establishing the significance of renin as a causative or contributory factor in hypertension or hyperaldosteronism in a particular patient For this purpose the novel peptides of the present invention may be administered in a single dose of from O11 to 10 mg per kg of body weight. Both in vivo and in vitro methods may be employed. In the in vivo method, a novel peptide of the present invention is administered to a patient, preferably by intravenous injection, although parenteral administration is also suitable, at a hypotensive dosage level and as a single dose, and there may result a transitory fall in blood pressure. This fall in blood pressure, if it occurs, indicates supranormal plasma renin levels. An in vitro method which may be employed involves incubating a body fluid, preferably plasma, with a novel peptide of the present invention and, after deproteinization, measuring the amount of angiotensin II produced in nephrectomized, pentolinium-treated rats. Another in vitro method involves mixing the plasma or other body fluid with a novel peptide of the present invention and injecting the mixture into a test animal. The difference in pressor response with and without added peptide is a measure of the renin content of the plasma. Pepstatin may be employed in the methods described above as an active control. See, e.g., U.S. Patent Nos. 3,784,686 and 3,873,681 for a description of the use of pepstatin in diagnostic methods of this type. The novel peptides of the present invention may be prepared in accordance with well-known procedures for preparing peptides from their constituent amino acids, which will be described in more detail below. Continued on page 21a A method of preparing a peptide of the formula: EMI22.1 wherein: A is hydrogen; EMI22.2 EMI22.3 where n is O to 5 and Rj has the same meaning as set out further below, and may additionally be hydrogen; 3 is absent; glycyl; sarcosyl; or EMI22.4 D is absent; or EMI22.5 where Z is (CH)n and n is l or 2; or -S-; Continued on page 21b R1 is hydrogen; C14 alkyl; hydroxy C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C24 alkyl; guanidyl C23 alkyl; or methylthiomethyl; R is hydrogen; C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3 is C36 alkyl; C3-7 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; R4 is hydrogen; or EMI23.1 where R6 is hydrogen; C14 alkyl; hydroxy; or C3 ¯7 cycloalkyl; and R2 is as defined above; R5 is hydrogen; EMI23.2 where R6 is hydrogen, C1-4 alkyl, hydroxy, or C37 cycloalkyl, and R is as defined above; or -CH2-R7 , where R7 is 4-imidazolyl, amino C2-4 alkyl, 2-, 3-, or 4-pyridyl, or guanidyl C2-3 alkyl; and 8 E is OR8; NHR8, or N(R where each R8 may be the same or different and is hydrogen or C14 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof said peptide being comprised of from five to nine amino acids identifies as I through IX, amino acids AA I being at the-C-terminus of said peptide, to which substituent E is attached, and amino acid AA V through IX being at the N-terminus of said peptide., to which substituent A is attached, comprises the steps of: : (a) treating the desired ester or amide of the C-terminus amino acid AA I with the next adjacent amino acid AA II of said peptide, the amino group of said amino acid being protected by a protecting group, in the presence of a condensing agent, whereby a dipeptide of the two amino acids AA I and II is formed; (b) deprotecting the dipeptide formed in step (a) by removing the protecting group from the amino group of AA II; (c) treating the dipeptide of AA I and AA II with AA III, the- amino group of which is protected by a protecting group, in the presence of a condensing agent, whereby a tripeptide of AA I, AA II and AA III is formed; (d) deprotecting the tripeptide formed in step (c) by removing the protecting group from the amino group of AA III; ; (e) forming a pentapeptide up to a nonapeptide of AA I, through AA V, AA VI, AA VII, AA VIII, or AA IX, by repeating the procedure of step (c) using protected AA IV through protected AA IX; (f) deprotecting the pentapeptide through nonapeptide formed in step (e) to give the peptide of formula I wherein A is hydrogen; and optionally Continued on page 21d (b) by transesterification with a C1 4 alkanol to give E equals OR8 where R8 equals C1-4 alkyl; (c) by ammonolysis with NH R8 or NH(R8)2 to give 82 8 E equals NHR8 or N(R 2 where R8 is hydrogen or C14 alkyl; removal of sidechain protecting groups being accomplished either before or after removal of the peptide of formula I from said synthetic resin substrate. The unusual amino acid, statine, may be prepared in accordance with the procedure described in Rich et. al., J. Org. Chem. 43: 3624 (1978). The novel inhibitory peptides of the present invention are prepared by using the solid phase sequential synthesis technique. In the following description several abbreviated designations are used for the amino acid components, certain preferred protecting groups, reagents and solvents. The meanings of such abbreviated designations are given below in Table I. Continued on page 22 (g) treating the pentapeptide through nonapeptide formed in step (f) with R3-o-CO-Y, or R3 -(CH2) n¯CO¯Y, where 3 R and n are as defined above and Y is an acid halide, anhydride, or other carboxyl activating group, to give the peptide of formula I wherein A is other than hydrogen; and optionally (h) hydrolyzing the pentapeptide through nonapeptide formed in steps (f) or (g) where an ester of AA I is employed, to give the peptide of formula I wherein E is OR8 and R8 is hydrogen; said method also comprising, where necessary, protection of sidechaim substituents of the component amino acids AA I through AA IX, with deprotection being carried out as a final step; said method also comprising any combination of the steps set out above, whereby the amino acids I through IX and substituents A and E are assembled in any desired order to prepare the peptide of formula I; and said method also comprising employment of the steps set out above in a solid phase sequential synthesis, whereby in the initial step the carboxyl group of the selected amino acid is bound to a synthetic resin substrate while the amino group of said amino acid is protected, followed by removal of the protecting group, the succeeding steps being as set out above, the peptide as it is assembled being attached to said synthetic resin substrate; followed by a final step of removing the peptide of formula I from said synthetic resin substrate: (a) by strong acid cleave to give E equals oR8 where R equals H, Continued on page 21e TABLE I Abbreviated Designation Amino Acid Ala L-alanine Arg L-arginine Gly L-glycine His D or L-histidine Ile L-isoleucine Leu L-leucine Lys L-lysine Met L-methionine Orn L-ornithine Phe L-phenylalanine Pro D or L-proline Sar L-sarcosine (N-methylglycine) Ser L-serine Sta (3S,4S)-statine Thr L-threonine Trp L-tryptophan Tyr L-tyrosine Val L-valine Abbreviated Protecting Designation Groups BOC tert-butyloxycarbonyl CBZ benzyloxycarbonyl DNP dinitrophenyl OMe methyl ester Abbreviated Activating Designation Groups HBT 1-hydroxybenzotriazole Abbreviated Condensing Designation Agents DCCI dicyclohexylcarbodiimide DPPA diphenylphosphorylazide Abbreviated Designation Reagents TEA triethylamine TFA trifluoroacetic acld Abbreviated Designation Solvents A ammonium hydroxide (conc.) AcOH acetic acid C chloroform DMF dimethylformamide E ethyl acetate M methanol P pyridine THF tetrahydrofuran W water The synthesis of the peptides of the-resent invention by the solid phase technique is cond-cted in a stepwise manner on chloromethylated resin. The resin is composed of fine beads (20-70 microns in diameter) of a synthetic resin prepared by copolymerization of styrene with 1-2 percent divinylbenzene. The benzene rings in the resin are chloromethylated in a Friedel-Crafts reaction with chloromethyl methyl ether and stannic chloride. The Friedel-Crafts reaction is continued until the resin contains 0.5 to 5 mmoles of chlorine per gram of resin. The amino acid selected to be the C-terminal amino acid of the linear peptide is converted to its amino protected derivative. The carboxyl group of the selected C-terminal amino acid is bound covalently to the insoluble polymeric resin support, as for example, as the carboxylic ester of the resin-bonded benzyl chloride present in chloromethylsubstituted polystyrene-divinylbenzene resin. After the amino protecting group is removed, the amino protected derivative of the next amino acid in the sequence is added along with a coupling agent, such as dicyclohexylcarbodiimide. The amino acid reactant may be employed in the form of a carboxyl-activated amino acid such as ONp ester, an amino acid azide, and the like. Deprotection and addition of successive amino acids is performed until the desired linear peptide is formed. The selection of protecting groups is, in part, dictated by particular coupling conditions, in part by the amino acid and peptide components involved in the reaction. Amino-protecting groups ordinarily employed include those which are well known in the art, for axa;e, u--evha..e protracting sbstituents such as benzyloxy-carbonyl (carbobenzoxy), p-methoxycarbo- benzoxy, p-nitrocarbobenzoxy, t-butyoxycarbonyl, and the like. It is preferred to utilize t-butyloxycarbonyl (BOC) for protecting the a-amino group in the amino acids undergoing reaction at the carboxyl end of said amino acid. The BOC protecting group is readily removed following such coupling reaction and prior to the subsequent step by the relatively mild action of acids (i.e. trifluoroacetic acid, or hydrogen chloride in ethyl acetate). The OH group of Thr and Ser can be protected by the Bzl group and the -amino group of Lys can be protected by the INOC group or the 2-chlorobenzyloxycarbonyl (2-CL-CBZ) group. Neither group is affected by TFA, used for removing BOC protecting groups After the peptide is formed, the protective groups, such as 2-C1-CBZ and Bzl, can be removed by treatment with HF or by catalytic hydrogenation. After the peptide has been formed on the solid phase resin, it may be removed from the resin by a variety of methods which are well known in the art. For example the peptide may be cleaved from the resin with hydrazine, by ammonia in methanol, or by methanol plus a suitable base. Preparation of the novel inhibitory peptides of the present invention utilizing the solid phase technique is illustrated in the following examples. EXAMPLE 1 N-Isobutyryl-L-histidyl-L-prolyl-L-phenylalanyl-L- histidvl-(3S,4S) -statyl-L-valyl-L-histidvl-L-qlvcYl amide The title peptide is prepared by standard solid phase methodology, as described in Erickson and Merrifield, Proteins, 3rd et., 2:257-527, 1976, using a Beckman Model 990B peptide synthesizer to carry out the operations according to the attached programs. The starting polymer is BOC-Gly esterified to 2% cross-linked polystyrene-divinylbenzene (6 mmol, 5.00 g) . The Na-BOC derivatives of His-DNP, Val, Sta, His-DNP, Phe, and Pro are coupled using dicyclohexylcarbodiimide with an equivalent of the additive l-hydroxybenzotriazole hydrate. The Sta is prepared in accordance with Rich et al., J. Org. Chem. 43:3624, 1978. The BOC-group is removed with 40% trifluoroacetic acid. A coupling of 60 minutes followed by a recoupling of 120 minutes (2.5 equivalents each time of BOC-amino acid) are used for each amino acid, except for Sta. These coupling times have been previously demonstrated to give complete coupling (as judged by the method of Raiser) in this sequence. In order to conserve the amounts of Sta employed, an initial coupling using 1.08 equivalents of Na-BOC-Sta (in 20 ml of 1:1 CH2C12/DMF) for 72 hrs gives approximately 958 complete reaction. The addition of an additional 0.12 equivalents of N-BOC-Sta plus an equal amount of DCCI to the stirring suspension gives complete coupling after an additional 18 hrs. The N-terminal isobutyryl group is coupled for 60 minutes as the symmetrical anhydride generated in situ from 5.0 equivalents of isobutyric acid and 2.5 equivalents of DCCI. This is followed by a recoupling for 120 minutes using 2.5 equivalents of isobutyric acid, HBT, and DCCI. The DNP protecting groups on His are removed in the final program using two 25-minute treatments with 10% thiophenol in DMF. Tfle tinisned resin-peptide is dried and suspended in 30 ml methanol containing 1 g ammonium acetate in a 100 ml pressure bottle containing a magnetic stirring bar. The suspension is cooled under nitrogen to -200C, and anhydrous ammonia is bubbled through the suspension until it is saturated. The pressure bottle is then closed and allowed to warm to room temperature. The suspension is stirred for 72 hrs, after which the pressure valve is carefully opened, allowing the ammonia to escape. The suspension of beads in orangered solution is filtered and the beads washed. The filtrate and washes are evaporated and the solid dried. This crude product is then partitioned between water (200 ml) and ethyl acetate (200 ml) The ethyl acetate layer is washed three times with 100 ml of a 1% citric acid solution. The product and the acid layer are neutralized with solid sodium hydrogencarbonate. A yellow oil precipitates from the water when it becomes basic. The now basic water solution and precipitated oil are extracted four times with 100 ml of dichloromethane, and the organic layers are dried and evaporated to give 6.4 g of crude yellow solid. This solid is dissolved in 50 ml of 80:20:2.5, chloroform/methanol/water and loaded onto a silica column (E. Merck No. 9385 silica, 0.040-0.063 mm particle size) 8.9x47 cm (ca. 1500 g silica gel) which has been packed in the same solvent. The column is eluted at 18 ml/min with the same solvent and, after 2700 ml, fractions are collected (27 ml each). The pure product is identified by TLC of the fractions. These fractions are combined and evaporated to a light yellow oil. The oil is dissolved in 300 ml of water. The solution is filtered (10 ij) and freeze dried to give the final product. TLC: 50:40:10 C/M/A Rf = 0.66 For all of the above no impurities are detected at the 2% level, i.e., the product is greater than 99% pure. HPLC: Greater than 99% single peak. Spinco: His 2.02 Pro 1.00 Phe 0.99 Val 0.99 Gly 0.99 SCHEDULE OF STEPS FOR 6 MMOL RUN Step So1ent/Reagent Vol. (ml) Mix time (min) Coupling Program 1 1 CH2C12 6 x 60 2 2 40% TFA in CH2Cl2 1 x 60 2 3 40% TFA in CH2C12 1 x 60 25 4 CH2C12 3 x 60 2 5 10% TEA in CH2Cl2 2 x 60 5 6 CH2C12 3 x 60 2 7 BOC-amino acid, HBT 40 5 in 1:1 DMF/CH2Cl2 8 1.OM DCCI in CH2C12 15 60 9 DMF 1 x 60 2 10 MeOH 2 x 60 2 11 CH2Cl2 1 x 60 2 Re-Coutle Program 2 1 CB2C12 1 x 60 2 2 10% TEA in CH2C12 2 x 60 5 3 2 2 3 x 60 2 4 BOC-amino acid, HBT 40 5 in 1: :1 DMF/CH2Cl2 5 l.0M DCCI in CH2C12 15 120 6 DMF 1 x 60 2 7 MeOH 2 x 60 2 8 CH2Cl2 5 x 60 2 Program 3 (DNP removal) 1 CH2Cl2 1 x 60 2 2 DMF 2 x 60 2 3 10% phenylthiol in DMF 1 x 60 25 4 DMF 1 x 60 2 5 10% TEA in CH2Cl2 1 x 60 2 6 DMF 2 x 60 2 7 10% phenylthiol in DMF l x 60 25 8 DMF 3 x 60 2 9 MeOH 2 x 60 2 10 CH2C12 2 x 60 2 11 MeOH 2 x 60 2 12 CH2C12 2 x 60 2 13 MeOH 2 x 60 2 EXAMPLE 2-6 Following the standard solid phase methodology described above in Example l, additional inhibitory peptides of the present invention are prepared, substituting equivalent amounts of the appropriate BOC-amino acid for those utilized in Example 1, and, where necessary, providing N-terminal groups as substitutes for the isobutyryl group in accordance with well established procedures in the art. The peptides prepared are set out in the following table wherein the subscribed numerical value for each amino acid indicates the results of the Spinco amino acid analysis. Example Peptide No. (5) 6 7 8 9 10(11) 12 13 (14) 2 TABU* - His - Pro - Phe - His - Sta - Ile - His - NH2 0.99 1.00 0.99 0.99 1.04 0.99 3 BOC - Phe - His - Sta - Ile - His - NH2 4 CBZ - Phe - His - Sta - Ile - His - NH2 5 IVA**- His - Pro - Phe - His - Sta - Ile - His - NH2 6 IVA - His - Pro - Phe - His - Sta - Leu - His - NH2 0.99 1.00 1.01 0.99 1.01 0.99 * IBU = iso-butyryl **IVA = iso-valeryl EXAMPLE 7 N- Isovaleryl-L-histidyl-L-prolyl.L-phenylalanyl-L- histidyl-(3S,4S) -statyl-L-leucYl-L-phenylalanine amide The title peptide was prepared by standard solid phase methodology, as described in Erickson and Merrifield, Proteins, 3rd et., 2: :257-527, 1976, using a Beckman Model 990B peptide synthesizer to carry out the operations according to the attached programs. The starting polymer was BOC-Phe esterified to 2% cross-linked polystyrene-divinylbenzene (6 mmol, 5.00 g). The N-BOC derivatives of Leu, Sta, His-DNP, Phe, and Pro were coupled using dicyclohexylcarbodiimide with an equivalent of the additive l-hydroxybenzotriazole hydrate. The Sta was prepared in accordance with Rich et al., J. Org. Chem. 43:3624, 1978. The BOC-group was removed with 40% trifluoroacetic acid. A coupling of 60 minutes followed by a recoupling of 120 minutes (2.5 equivalents each time of BOC-amino acid) were used for each amino acid, except for Sta. These coupling times had been previously demonstrated to give complete coupling (as judged by the method of Kaiser) in this sequence. In order to conserve the amounts of Sta employed, an initial coupling using 1.08 equivalents of N -BOC-Sta (in 20 ml of 1:1 CH2C12/DMF) for 72 hrs gave approximately 95% complete reaction. The addition of an additional 0.12 equivalents of N&alpha;-BOC-Sta plus an equal amount of DCCI to the stirring suspension gave complete coupling after an additional 18 hrs. The N-terminal isovaleryl group was coupled for 60 minutes as the symmetrical anhydride generated in situ from 5.0 equivalents of isovaleric acid and 2.5 equivalents of DCCI. This was followed by a recoupling for 120 minutes using 2.5 equivalents of isovaleric acid, HBT, and DCCI. The DNP protecting groups on His were removed in the final program using two 25-minute treatments with 10% thiophenol in DMF. The finished resin-peptide was dried and suspended in 30 ml methanol containing 1 g ammonium acetate in a 100 ml pressure bottle containing a magnetic stirring bar. The suspension was cooled under nitrogen to -20 C, and anhydrous ammonia was- bubbled through the suspension until it was saturated. The pressure bottle was then closed and allowed to warm to room temperature. The suspension was stirred for 72 hrs, after which the pressure valve was carefully opened, allowing the ammonia to escape. The suspension of beads in orange-red solution was filtered and the beads washed. The filtrate and washes were evaporated and the solid dried. This crude product was then partitioned between water (200 ml) and ethyl acetate (200 ml). The ethyl acetate layer was washed three times with 100 ml of a 1% citric acid solution. The product and the acid layer were neutralized with solid sodium hydrogencarbonate. A yellow oil precipitated from the water when it became basic. The now basic water solution and precipitated oil were extracted four times with 100 ml of dichloromethane, and the organic layers were dried and evaporated to give 6.4 g of crude yellow solid. This solid was dissolved in 50 ml of 80:20:2.5:1, chloroform/methanol/water/acetic acid and loaded onto a silica column (E. Merck No. 9385 silica, 0.040-0.063 mm particle size) 8.9x47 cm (ca. 1500 g silica gel) which had been packed in the same solvent. The column was eluted at 18 ml/min with the same solvent and, after 2700 ml, fractions were collected (27 ml each) . The pure product was found in fractions 70-110. These fractions were combined and evaporated to a light yellow oil. The oil was dissolved in 20 ml of acetic acid and 300 ml of water were added. The solution was filtered (10 1,) and freeze dried to give 4.45 g of light yellow powder. TLC: 80:20:2 C/M/W Rf = 0.25 80:20:2:1 C/M/W/AcOH Rf = 0.25 80:20:2 C/M/A Rf = 0.51 10:5:1:3 E/P/AcOH/W Rf = 0.38 For all of the above no impurities were detected at the 1% level, i.e., the product was greater than 99% pure. EiSLC; - er ''.an 99 single peak. Spinco: His 1.96 89.4% peptide based Pro 1.01 on mol. wt. 1037.3 Phe 2.00 100% based on Sta 1.02 for. wt. 1157.4 Leu 1.02 NH3 NMR: NH3 1.25 1H NMR: 300 MHz spectrum consistent with structure proposed; no unexpected peaks. SCHEDULE OF STEPS FOR 6 MMOL RUN Step Solvent/Reagent Vol. (ml) Mix time (min) Coupling Program 1 I CH2C12 6 x 60 2 2 40% TFA in CH2C12 1 x 60 2 3 40% TFA in CH2C12 1 x 60 25 4 CH2C12 3 x 60 2 5 10% TEA in CH2C12 2 x 60 5 6 CH2C12 3 x 60 2 7 BOC-amino acid, HBT 40 5 in 1:1 DMF/CH2Cl2 8 1.OM DCCI in CH2Cl2 15 60 9 DMF 1 x 60 2 10 MeOH 2 x 60 2 11 CH2C12 1 x 60 2 Re-Couple Program 2 1 C 2 12 1 x 60 2 2 10% TEA in CH2C12 2 x 60 5 3 CH2C12 3 x 60 2 4 BOC-amino acid, HBT 40 5 in 1: :1 DMF/CH2C12 5 1.OM DCCI in CH2Cl2 15 120 6 DMF 1 x 60 2 7 MeOH 2 x 60 2 8 CH2Cl2 5 x 60 2 Program 3 (DNP removal) 1 CH2C12 1 x 60 2 2 DMF 2 x 60 2 3 10% phenylthiol in DMF 1 x 60 25 4 DMF 1 x 60 2 5 10% TEA in CH2Cl2 1 x 60 2 6 DMF 2 x 60 2 7 10% phenylthiol in DMF 1 x 60 25 8 DMF 3 x 60 2 9 MeOH 2 x 60 2 10 CH2C12 2 x 60 2 11 MeOH- 2 x 60 2 12 CH2C12 2 x 60 2 13 MeOH 2 x 60 2 EXAMPLE 8-43 Following the standard solid phase methodology described above in Example 7, additional inhibitory peptides of the present invention were prepared, substituting equivalent amounts of the appropriate BOC-amino acid for those utilized in Example 7, and, where necessary, providing N-terminal groups as suostitutes for the isovaleryl group in accordance with well established procedures in the art. The peptides prepared are set out in the following table, wherein the subscribed numerical value for each amino acid indicates the results of the Spinco amino acid analysis. Example Peptide No. (5) 6 7 8 9 10(11) 12 13 (14) 8 H - His - Pro -.Phe - His - Sta - Leu - Phe - NH2 1.01 1.04 1.01 1.01 0.97 0.95 1.01 9 BOC - His - Pro - Phe - His - Sta - Leu - Phe - NH2 1.02 1.04 0.98 1.02 0.98 0.98 10 IBU*- His - Pro - Phe - His - Sta - Leu - Phe - NH2 11 BOC - Pro - His - Pro - Phe - His - Sta - Leu - Phe - NH2 1.04 0.97 1.04 1.02 0.97 0.99 1.00 1.02 12 H - Pro - Phe - His - Sta - Leu - Phe - NH2 1.04 1.08 0.94 0.90 0.95 1.08 : 13 Acetyl - Pro - Phe - His - Sta - Leu - Phe - NE2 0.98 1.00 1.00 1.02 1.00 14 BOC - Pro - Phe - His - Sta - Leu - Phe - NH2 1.09 1.04 0.95 0.94 0.93 1.04 15 Phenoxyacetyl - Pro - Phe - His - Sta - Leu - Phe - NH2 1.02 1.00 0.99 0.99 1.00 16 H - Phe - His - Sta - Leu - Phe - NH2 0.98 1.00 1.03 0.99 17 BOC - Phe - His - Sta - Leu - Phe - NH2 0.98 0.99 1.06 0.98 18 Cyclopentylcarbonyl - Phe - His - Sta - Leu - Phe - NH2 1.02 0.91 1.04 1.02 19 IBU - His - Pro - Phe - Ala - Sta - Leu - Phe - NS2 0.99 0.98 1.01 0.98 1.02 1.01 20 IBU - His - Pro - Ala - Phe - Sta - Leu - Phe - NH2 0.95 0.98 0.99 1.04 1.00 1.04 21 80 C - His - Pro - Phe - Phe - Sta - Leu - Pne - NH2 1.01 0.98 1.00 1.00 1.02 1.00 22 IBU - His - Pro - Phe - His - Sta - Gly - Phe - NH2 0.94 1.11 1.00 0.94 1.02 1.00 23 IBU - His - Pro - Phe - His - Sta - Ala - Phe - Nh2 1.02 0.96 1.00 1.02 1.00 1.00 24 IBU - His - Pro - Phe - His - Sta - Val - Phe - NH2 25 BOC - His -'Pro - Phe - His - Sta - Ile - Phe - NH2 1.01 0.99 1.00 1.01 1.00 0.97 1.00 26 SOC - His - Pro - Phe - His - Sta - Phe - Phe - NH2 1.04 1.05 0.98 1.04 0.92 0.98 0.98 Cyclohexyl27 IBU - His - Pro - Phe - His - Sta - Ala - Phe - NH2 1.00 0.98 1.01 1.00 1.01 28 BOC - His - Pro - Phe - His - Sta - Leu - Leu 1.04 1.00 0.97 1.04 1.00 0.98 0.38 29 BOC - His - Pro - Phe - His - Sta - Leu - Tyr - H2 0.99 1.04 0.99 0.99 0.97 1.08 1.13 30 BOu - Phe - His - Sta - Leu - Tyr 1.00 1.00 1.00 31 BOC - Phe - His - Sta - Leu - Ala - OCH3 1.00 1.01 1.01 0.98 32 IVA**- His - Pro - Phe - His - Sta - Leu - Phe - OH 33 B0C - His - Pro - Phe - His-- Sta - Leu - Phe - OCH3 1.01 1.02 0.99 1.01 1.05 0.93 0.99 34 IBU - His - Pro - Phe - His - Sta - Leu - Phe - Gly - OH 1.02 0.97 1.01 1.02 0.99 1.01 0.98 35 IBU - His - Pro - Phe - His - Sta - Leu - Phe - Gly - OCH3 1.02 0.97 1.01 1.02 0.99 1.01 0.38 36 BOC - His - Pro - Phe - His - St - Leu - Leu - Phe - SH. 0.98 0.95 1.03 0.98 1.02 1.01 1.01 1.03 37 IBU - His - Pro - Phe - His - Sta - Leu - Phe - Lys - SH2 1.01 1.03 0.99 1.01 1.00 0.99 1.03 38 Sar - Pro - Phe - His - Sta - Leu - Phe - NH2 0.99 0.99 1.00 1.01 1.02 0.99 39 D - His - Pro - Phe - His - Sta - Leu - Phe - NH2 0.98 1.02 1.00 0.98 1.04 1.00 40 IVA - His - D - Pro - Phe - His - Sta - Leu - Phe - NM2 1.00 0.98 0.99 1.00 1.07 0.99 41 BOC - His - Pro - o - I - Phe - His - Sta - Leu - Phe - NH2 0.98 1.01 0.98 1.02 1.01 42 BOC - His - Pro - Phe - - T - Phe - Sta - Leu - Phe - NH2 0.98- 0.97 1.01 1.03 1.01 43 IVA - His - Pro - Phe - His - Sta - Leu - Val - Phe - NH2 1.01 1,02 1.00 1.01 1.00 0.95 1.00 *IBU = iso-butyryl **IVA = <RTI ID=42.6> iso-valeryl For the peptides preparea above, various analytical methods were carried out to verify the structure of the peptide products. The following table indicates which methods were employed and summarizes the results where practicable. Example Analytical Method No. TLC1 HPLC2 AA3 NMR4 EA5 (No. of systems) 2 97% (3) 95.7% X X X 6 97% (3) 95.3% X X X 8 95% (3) 93.2% X 9 95% (2) 92.4% X 10 99% (3) X X X 11 98% (2) 98.88 X 12 90% (2) ¯¯¯¯¯ X 13 95% (2) 94.2% X X 14 98% 94% X 15 97% (2) 90% X 16 97% (2) 92.3% X X 17 97% 88% X ¯ X 18 908 80% X X 19 98% (2) 90.5% X X X 20 95% (2) 96.6% X X X 21 95% (2) 95% X 22 97% 90% X 23 99% (2) 99% X X X 24 98% (3) 96.1% X ¯ X 25 98% ¯¯¯¯¯¯ X 26 95% (2) 96.7% X X 27 95% (2) 98% X X X 28 95% 94.1% X 29 95% (2) ¯¯¯¯¯ X 30 95% 95% X X 31 95% 98% X X 32 95% (3) 80% ¯ X 33 98% 99% X 34 98% (2) 96.7% X X 35 97% (3) 95.8% X X 36 98% 98% X 37 99% (3) 95.0% X x 38 95% (2) 97.0% X X X 39 95% (2) 94.7% X X 40 95% (2) 93.6% X X X 41 95% (2) 95.3% X X X 42 95% (2) 94.0% X X X 43 95% (2) 98.3% X X X TLC = thin layer chromatography on silica gel; visualization by reagents which tend to detect peptides; no. of systems refers to number of different sovlent mixtures used to elute chrornatograms; 9s refers to estimated purity. 2HPLC = high pressure liquid chromatography; detection by ultraviolet absorption at 240 nm or 210 nm; chromatography is reverse phase, i.e., non-polar elution from non-polar support; î refers to purity, but method tends to overestimate non-peptide impurities. 3AA = amino acid analysis; peptides are hydrolyzed to their component amino acids, which are then quantitatively measured; values should be 1.00 + 0.03. 4NMR = nuclear magnetic resonance spectroscopy at 300 MHz or 360 MHz for protons; X = spectrum consistent with structure; ¯¯¯ = not performed. 5EA = elemental analysis for C, H, and N; X = analysis consistent with structure plus added solvent; - = not performed. EXAMPLE 44 Hog Renin Inhibition An assay was carried out in order to determine the inhibitory potency of the peptides of the present invention. The assay measured the inhibition of hog kidney renin, and was in accordance with the procedure described in Rich et al., J. Med. Chem. 23:27, 1980, except that a pH of 7.3 was used. The results of the assay, illustrated in the table below, are expressed as I50 values, which refers to the concentration of peptide inhibitor necessary to produce 50% inhibition of renin activity. This I50 value is obtained typically by plotting data from four inhibitor concentrations. Pepstatin was used as an active control. Peptide I50(M) H-His-Pro-Phe-His-Sta-Leu-Phe-NH2 2.0x10 -8 iso-Valeryl-His-Pro-Phe-His-Sta-Leu-Phe-NH2 3.0x10 8 Acetyl-Pro-Phe-His-Sta-Leu-Phe-NH2 3.7x10 -8 Acetyl-Phe-His-Sta-Leu-Phe-NH2 -8 BOC-Phe-His-Sta-Leu-Phe-NH2 3.6-10 -8 BOC-His-Pro-Phe-Phe-Sta-Leu-Phe-NH2 2.0x10-8 IBU-His-Pro-Phe-His-Sta-Ala-Phe-NH2 3. 7x10 IBU-His-Pro-Phe-His-Sta-Ala-Phe-NH2 2.0x10 BOC-His-Pro-Phe-His-Sta-Leu-Leu-OCH3 2.3x10-8 BOC-His-Pro-Phe-His-Sta-Leu-Tyr-NH2 2.6x10-8 IBU-His-Pro-Phe-His-Sta-Leu-Phe-Lys-NH2 2.3x10-8 6. 6x10-8 Sar-Pro-Phe-His-Sta-Leu-Phe-NH2 6.6x10-8 D-His-Pro-Phe-His-Sta-Leu-Phe-NH2 4.9x10 IVA-His-D-Pro-Phe-His-Sta-Leu-Phe-NH2 5.8x10 BOC-His-Pro-o-I-Phe-His-Sta-Leu-Phe-NH2 4.2x10-8 -9 BOC-His-Pro-Phe-E-I-Phe-Sta-Leu-Phe-NH2 8.1x10 IVA-His-Pro-Phe-His-Sta-Leu-Val-Phe-NH2 4.6x10-8 Pepstatin (iso-valeryl-Val-Val-Sta-Ala-Sta) 1.0x10 6 EXAMPLE 45 Hog Renin and Human Renin Inhibition In order to illustrate the correlation between hog renin inhibition and human renin inhibition by a single peptide entity, four of the peptic inhibitors evaluated in te og renin inhibition assay described above in Example 44 were further evaluated in human renin assay based on themethod of Haber et al., J. Clin. Endocrinol. 29:1349, 1969. This method employs a radioimmunoassay technique to measure the amount of angiotensin I product of renin cleavage of its substrate. Human plasma (lyophilized) was used as the source of human substrate and human renin. I50 values were obtained by plotting data at several inhibitor concentrations. The comparative results are illustrated below. Pepstatin was used as an active control. Peptide I50(M) Hog renin Human renin iso-Valeryl-His-Pro-Phe-His- 3.0x10 1.8x10 8 Sta-Leu-Phe-NH2 iso-Butyryl-His-Pro-Phe-His-- 3.7x10 4.2x10 8 Sta-Ala- Phe-NH2 iso-Butyryl-His-Pro-Phe-His- 5.4x10-7 7.3x10 -8 Sta-Val-His-Gly-NH2 iso-Valeryl-His-Pro-Phe-His - Sta-Ile-His-NH2 9.3x10-7 7.3x10-9 Pepstatin(iso-valeryl-Val- 1.0x10-6 > > 1.0x10-6 Val-Sta-Ala-Sta) (20% inhibition at 1.0x10 -6)

Claims: WHAT IS CLAIMED IS: 1. A peptide of the formula: EMI47.1 wherein: A is hydrogen; EMI47.2 EMI47.3 where n is O to 5 and R has the same meaning as set out further below, and may additionally be hydrogen; B is absent; glycyl; sarcosyl; or EMI47.4 D is absent; or EMI47.5 where Z is (CH2)n and n is 1 or 2 ; or -S-; R1 is hydrogen; C14 alkyl; hydroxy C14 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C2-4 alkyl; guanidyl C2-3 alkyl; or methylthiomethyl; R is hydrogen; C14 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3is C3-6 alkyl; C37 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; 4. R4 is hydrogen; or EMI48.1 where R6is hydrogen; C14 alkyl; hydroxy; or C3-7 cycloalkyl; and Rê is as defined above; R5 is hydrogen; EMI48.2 where R6 is hydrogen, C14 alkyl, hydroxy, or C3-7 cycloalkyl, 2. and R is as defined above; or -CH2 R7, where R7 is 4-imidazolyl, amino C2-4 alkyl, 2-, 3-, or 4-pyridyl, or guanidyl C2 3 alkyl; and E is OR8; NHR8, or N(R8), where each R8 2 may be the same or different and is hydrogen or C14 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. 2. A peptide. according to Claim 1 wherein the peptide is iso-butyryl-His-Pro-Phe-His-Sta-Val- His-Gly-NH2* 3. A peptide according to Claim 1 wherein the peptide is iso-butyryl-His-Pro-Phe-His-Sta-Ile His-NH2. 4. A peptide according to Claim 1 wherein the peptide is tert-butyloxycarbonyl-Phe-His-Sta Ile-His-NH2. 5. A peptide according to Claim 1 wherein the peptide is benzyloxycarbonyl-Phe-His-Sta-Ile- His-NH2. 6. A pharmaceutical composition for treating renin-associated. hypertension, comprising a pharmaceutical carrier and a therapeutically effective amount. of a peptide of the formula: EMI49.1 wherein: A is hydrogen; EMI50.1 EMI50.2 where n is 0 to 5 and R' has the same meaning as set out further below, and may additionally be hydrogen; B is absent; glycyl; sarcosyl; or EMI50.3 D is absent; or EMI50.4 where Z is (CH2) n and n is 1 or 2; or -S-; 1-4 kyl; hydrogen; C14 alkyl; hydroxy C alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C24 alkyl; guanidyl C2-3 alkyl; or methylthiomethyl; R is hydrogen; C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3 is C36 alkyl; C37 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; R4 is hydrogen; or -CH-R6, where R6is R hydrogen; C14 alkyl; hydroxy; or C37 cycloalkyl; and R2 is as defined above; R5 is hydrogen; EMI51.1 where R6 is hydrogen, C1-4 alkyl, hydroxy, or C37 cycloalkyl, and R2 is as defined above; or -CH2-R where R7 is 4-imidazolyl, amino C 2-4 alkyl, 2-, 3-, or 4-pyridyl, or guanidyl C23 alkyl; and E is OR8; NHR8, or N(R 2' where each R8 may be the same or different and is hydrogen or C1-4 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. 7. A pharmaceutical composition for treating renin-associated hyperaldosteronism, comprising a pharmaceutical carrier and a therapeutically effective amount of a peptide of the formula EMI52.1 wherein: A is hydrogen; EMI52.2 EMI52.3 where n is 0 to 5 and R has the same meaning as set out further below, and may additionally be hydrogen; B is absent; glycyl; sarcosyl; or EMI52.4 D is absent; or EMI52.5 where Z is (CH2) n and n is I or 2; or -S-; R is hydrogen; C14 alkyl; hydroxy C14 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C2-4 alkyl; guanidyl C23 alkyl; or methylthiomethyl; R2 is hydrogen; C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3 is C36 alkyl; C37 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; R is hydrogen; or EMI53.1 where 6 is hydrogen; C1-4 alkyl; hydroxy; or C3-7 7 cycloalkyl; R5 is hydrogen; EMI53.2 where R6 is hydrogen, C1-4 alkyl, hydroxy, or C37 cycloalkyl, and R2 is as defined above; or -CH -R7, where R7 is 4-imidazolyl, amino 2-4 alkyl, 2-, 3-, or 4-pyridyl, or guanidyl C23 alkyl; and E is OR8; NHR8, or N(R8) 2 where each R8 may be the same or different and is hydrogen or C14 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof. CLAIMS FOR AUSTRIA 1. A method of preparing a peptide of the formula: EMI54.1 wherein: A is hydrogen; EMI54.2 EMI54.3 where n is 0 to 5 and R' has the same meaning as set out further below, and may additionally be hydrogen; B is absent; glycyl; sarcosyl; or EMI54.4 D is absent; or EMI54.5 where Z is (CH2) and n is 1 or 2; or -S-; R1 is hydrogen; C1-4 alkyl; hydroxy C1-4 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; indolyl; 4-imidazolyl; amine C 2-4 alkyl; guanidyl C2-3 alkyl; or methylthiomethyl; R2 is hydrogen; C14 alkyl; phenyl; phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; or indolyl; R3 is C36 alkyl; C37 cycloalkyl; phenyl; or phenyl mono-substituted with a member selected from the group consisting of methyl, trifluoromethyl, hydroxy, methoxy, fluoro, chloro, bromo, and iodo; R4 is hydrogen; or EMI55.1 where R6 is hydrogen; C14 alkyl; hydroxy; or C37 cycloalkyl; and R2 is as defined above; R5 is hydrog1en;. EMI55.2 where R6 is hydrogen, C14 alkyl, hydroxy, or C37 cycloalkyl, and R2 is as defined above; or 7 7 -CH2-R , where R is 4-imidazolyl, amino C24 alkyl, 2-, 3-, or 4-pyridyl, or guanidyl C2-3 alkyl; and 8 E is OR NHR8, or N(R 2' where each R8 R8 may be the same or different and is hydrogen or C1-4 alkyl; wherein all of the asymmetric carbon atoms have an S configuration, except those of substituents B and D, which may also have the R configuration; and a pharmaceutically acceptable salt thereof said peptide being comprised of from five to nine amind acids identified as I through IX, amino acids AA I being at the C-te¯:r.ln.s of said peptide. to which slrase Qne E is attached, and amino acid AA V through IX being at the N-terminus of said peptide, to which substituent A is attached, compris.ing the steps of: : (a) treating the desired ester or amide of the C-terminus amino acid AA I with the next adjacent amino acid AA II of said peptide, the amino group of said amino acid being protected by a protecting group, in the presence of a condensinq agent, whereby a dipeptide of the two amino acids AA I and II is formed; (b) deprotecting the dipeptide formed in step (a) by removing the protecting group from the amino group of AA II; (c) treating the dipeptide of AA I and AA II with AA III, the amino group of which is protected by a protecting group, in the presence of a condensing agent, whereby a tripeptide of AA I, AA II and AA III is formed; (d) deprotecting the tripeptide formed in step (c) by removing the protecting group from the amino group of AA III; ; (e) forming a pentapeptide up to a nonapeptide of AA I, through AA V, AA VI, AA VII, AA VIII, or AA IX, by repeating the procedure of step (c) using protected AA IV through protected AA IX; (f) deprotecting the pentapeptide through nonapeptide formed in step (e) to give the peptide of formula I wherein A is hydrogen; and optionally (g) treating the pentapeptide through nonapeptide formed 3 in step (f) with R3-O-CO-Y, or R (CH,) -CO-Y, where 3 R lnXd n are as defined above and Y is an acid halide, anhydride, or other carboxyl activating group, to give the peptide of formula I wherein A is other than hydrogen; and optionally (h) hydrolyzing the pentapeptide through nonapeptide formed in steps (f) or (g) where an ester of AA I is employed, to give the peptide of formula I wherein E is OR8 and R8 is hydrogen; said method also comprising, where necessary, protection of sidechain substituents of the component amino acids AA I through AA IX, with deprotection being carried out as a final step; said method also comprising any combination of the steps set out above, whereby the amino acids I through IX and substituents A and E are assembled in any desired order to prepare the peptide of formula I; and said method also comprising employment of the steps set out above in a solid phase sequential synthesis, whereby in the initial step the carboxyl group of the selected amino acid is bound to a synthetic resin substrate while the amino group of said amino acid is protected, followed by removal of the protecting group, the succeeding steps being as set out above, the peptide as it is assembled being attached to said synthetic resin substrate; followed by a final step of removing the peptide of formula I from said synthetic resin substrate: (a) by strong acid cleavage to give E equals OR8 where R8 equals H, (b) by transesterification with a C1-4 alkanol to OR8 where R8 equalas where 1-4 give E equals or where R8 equals C1-4 alkyl; or (c) by ammonolysis with NH R8 or NH(R8) 2 to give E equal or N(R8)2 8 E equals NHR8 or N(R 2C1-4 alkyl; or C 1-4 alkyl; removal of sidechain protecting groups being accomplished either before or after removal of the peptide of formula I from said synthetic resin substrate. 2. The method of claim 1 for preparing the peptide iso-butyryl-His-Pro-Phe-His-Sta-Val-His- & y-NH2. 3. The method of claim 1 for preparing the peptide iso-butyryl -His-Pro-Phe-His-Sta-Ile-His-NH2. 4. The method of claim 1 for preparing the peptide tert-butyloxycarbonyl-Phe-His-Sta-Ile-His-NH2. 5. The method of claim 1 for preparing benzyloxycarbonyl Phe-His-Sta-Ile-His-NH2.

Inventors: BOGER, JOSHUA S., VEBER, DANIEL F.
Applicants: MERCK & CO. INC.
Application year: 1982
Main classification: C07K7
IPC codes: C07K5, C07K7, A61K38