GB1559610A - Synthesis of peptides - Google Patents

Description

(54) SYNTHESIS OF PEPTIDES (71) We, ARMOUR PHARMACEUTICAL COMPANY, (a Delaware corporation), of Greyhound Tower, Phoenix, Arizona 85077, U. S. A., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- The present invention relates to peptides and particularly resin peptides which are useful in the production of biologically active peptides and to their synthesis.

It has long been known that certain biologically active substances can be obtained from the glands of animals and these substances can be used in the treatment of deficiencies of the human body. One such substance is the parathyroid hormone, commonly called PTH, which for many years has been obtained from the parathyroid glands of animals, particularly porcine and bovine parathyroid glands.

The burden of having to collect the relatively small parathyroid glands of animals at the time the animals are slaughtered, the limitation of the quantity of such glands which can be collected and the extensive purification procedures which are required to produce peptides which can be administered to humans, are formidable disadvantages to the preparation of natural peptide hormones from animal glands.

The human parathyroid hormone (HPTH) has been identified as having a sequence of 84 amino acids, its amino-terminal 1-34 sequence having the following structure : H-Ser-Val-Ser-Glu-Ile-Gln-Leu-Met-His-Asn-Leu-Gly-Lys-His-Leu-Asn-Ser-Met 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Glu-Arg-Val-Glu-Trp-Leu-Arg-Lys-Lys-Leu-Gln-Asp-Val-His-Asn-Phe-OH 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Abbreviations Phe, Asn, His, etc. represent the different amino acid groupings in the peptide chain and the numbers represent the positions of the amino acid groups in the chain according to accepted nomenclature. See the article by Niall et al., in Proc. Nat.

Acad, Sci, U. S. A., 71,384-388 (1974). This fragment appears to have full biological activity when compared with the full molecule.

We are aware of disclosures of certain laboratory methods for the synthesis of certain peptides of relatively short amino acid chain lengths. These include an article by R. B. Merrifield entitled"Solid Phase Peptide Synthesis I"."The Synthesis of a Tetrapeptide"at pages 2149 to 2154 in Vol. 85 of Journal of the American Chemical Society (1963) and a book entitled"Solid Phase Peptide Synthesis"by John W.

Stewart and Janis D. Young published by W. H. Freeman and Company of San Francisco, California, but find in these publications no disclosures of resin peptides having amino groups of the kind and in the sequence involved in the present invention.

Accordingly the present invention provides a resin peptide containing the structure

wherein : (R) is an insoluble polystyrene resin ; W is a carbobenzyloxy, tosyl or 2,4-dinitrophenyl group; Bz is a benzyl, p-methoxybenzyl, p-chlorobenzyl, p-nitroben2yl or benzhydryl group; and TFA is a trifluoroacetyl group.

The present invention provides in further aspects :- (i) a synthetic peptide containing the structure: -Lys-Leu-Gln-Asp-Val-His-Asn-Phe- ; (ii) a synthetic peptide as in (i) above, having the formula

Val-His-Asn-Phe-OH wherein TFA is a trifluoroacetyl group; (iii) a synthetic peptide as in (i) above having the formula:

Gln-Asp-Val-His-Asn-Phe-OH wherein: TFA is a trifluoroacetyl group; (iv) a process for synthesizing a resin peptide which comprises coupling, P-Ser (Bz)-OH or P-D-Ser (Bz)-OH to

to produce a resin peptide having the structure :-

respectively, wherein (R), W, Bz and TFA are as defined above, T is a tosyl or nitro group and P is t-butyloxycarbonyl, amyloxycarbonyl or o-nitrophenylsulphenyl; (v) a process as in (iv) above which further comprises removing P from the structure obtained; (iv) a process as in (v) above which further comprises contacting the reaction product of (v) above with anhydrous hydrogen fluoride to remove the (R)-CH2, Bz, T and W groups and to produce a synthetic peptide as in (ii) or (iii) above; and (vii) a process as in (vi) above which further comprises contacting the reaction product of (vi) above with an aqueous base to remove the TFA group therefrom.

The total synthesis involves many rections by which many new intermediate resin peptides are formed and we will proceed with the description step by step, giving the structural formula, the general description and specific examples.

Preferably we use a solid phase synthesis whereby an insoluble polystyrene resin, obtained by catalytic polymerization of styrene and divinyl benzene is chloromethylated.

Firstly phenylamine is coupled to the chloromethylated resin, then asparagine and the other amino acids of the chain, in prescribed sequence, using a system of protection and deprotection of the active amine and carboxyl groups. Following the coupling g of the last amino acid in the chain, the resin is cleaved from the peptide chain and the remaining protective groups removed. AH amino acids are the naturally occurring L-isomers unless specifically defined.

The invention is further illustrated by the following Examples.

Preparation of Insoluble Resin By the term"insoluble resin" (hereinafter identified by the symbol (R) is meant a polymeric material which is insoluble in, but solvated and penetrated by, the solvents used in peptide synthesis and is capable of providing an active receptor site for the first amino acid coupled thereto, namely, phenylalanine.

In practice, it is preferable to use an insoluble polystyrene resin obtained by the catalytic polymerization of styrene and divinyl benzene. The resin is chloromethylated using chloromethyl methyl ether and stannic chloride catalyst according to the following reaction formula:

The chloromethylation reaction is specifically illustrated by the following example 1.

EXAMPLE 1 One Kg of 2% by volume divinylbenzene crosslinked polystyrene resin 200-400 mesh U. S. Bureau of Standards was washed with three 2 liter portions of methylene chloride. Fine particles were removed by draining the methylene chloride off the bottom each time. The resin was washed with two liters of the following solvents by suspension, stirring for ten minutes and filtration on a sintered glass Buchner: Two portions tetrahydrofuran, 2 portions water, 1 portion normal sodium hydroxide, 2 portions water, 2 portions dimethylformamide, 2 portions dioxane and 3 portions methanol. This washed resin was dried under vacuum at 60 C.

Five hundred grams of this washed polystyrene resin was stirred with 5 liters of chloromethyl methyl ether at room temperature and then the temperature was lowered to 0-5 C with an ice-water bath. Seventy-five grams of anhydrous stannic chloride in 925 ml ice-cold chloromethyl methyl ether was added and the mixture stirred in the ice-bath for 2 hours. The resin was filtered on a sintered glass Buchner and then washed with 2 liter portions of the following solvents: 25% by volume water in dioxane, 25% by volume two normal hydrochloric acid in dioxane, water and twice with methanol The washed resin was dried under vacuum at 45-50 C. By this method the usual chloride content is between 0.7 to 1.0 milli-equivalent per gram.

Phenylalanine Esterification to the Polystyrene Resin In the synthesis phenylalanine is first bonded to the polystyrene resin. This is described by the following formula :

. i 1/\ XH \--/Coupling @oCs2C1 HOOC-C-CH2 ' V 1 0 1 Reaction t No. I 0 H I ) ! i) == 1 NH r where (R) is polystyrene resin, BA is a suitable base such as triethylamine, diisopropyl- amine, diisopropylethylamine, or alkali metal salt, and"P"is an amino protective group which preferably is tertiary-butyloxycarbonyl (BOC) but may be amyloxy- carbonyl (AMOC) or ortho-nitrophenylsulfenyl (NPS).

As illustrated by the above formula the tert-butyloxycarbonyl-L-phenylalanine is attached to the chloromethylated resin in the presence of an acid acceptor. This reaction is demonstrated by the following specific Example 2.

EXAMPLE 2 Fifty grams of chloromethylated polystyrene resin, prepared as illustrated previously with a chlorine content of 0.74 milliequivalent (meq) per gram (37 meq chlorine) and 19.6 grams BOC-L-phenylalanime (74 meq) was stirred in 150 ml of absolute ethyl alcohol and then 9.77 mi of triethylamine (72 meq) was added and the mixture refluxed with stirring for 24 hours. The mixture was cooled, filtered on a sintered glass Buchner and washed on the Buchner with 500 ml portions of the following solvents: 2 times with 3A denatured alcohol, 2 times with dioxane, 2 times with 3A denatured alcohol, 2 times with water, 2 times with methanol. The resin was dried under vacuum at 495oC. Nitrogen analysis will show values varying from about 0.50 to 0.70 meq per gram. When the BOC protecting group was removed with trifluoroacetic acid as hereinafter described and the resin titrated to determine the available terminal amine group, this sample was found to approximate 0.38 meq per gram.

Deprotection and Neutralization

0 H Hox 1. Acid -CH=-0-C-C-N-f O ff2-0-C-C-NHZ 7. ! au Q2'H2 \ This resulting product is designated"Compound No. 1".

The deprotection of the amine function of the phenylalanine is accomplished by the removal of the protecting group using a suitable acid such as trifluoroacetic acid or hydrochloric acid. The resulting amine salt is then neutralized by treatment with a strong organic base. A specific example of this procedure is given in the following Example 3.

EXAMPLE 3 A 6 gram sample of the BOC-phenylalanine resin, as prepared by Example 2, was placed in the reaction vessel of a peptide synthesizer. The sample was washed twice with 40 ml portions of methylene chloride for two minutes each. Forty (40) ml of 50% by volume trifluoroacetic acid in methylene chloride was added and the mixture reacted for 30 minutes. After filtration the resin was washed with three 40 ml portions of methylene chloride, 2 portions of methanol and 3 portions of chloroform, each wash being of 2 minute duration. Neutralization was accomplished by a 5 minute reaction with 40 ml of a 10% by volume solution of diisopropylamine in chloroform. The resin was then washed 3 times with 40 ml of chloroform and 3 times with 40 ml of methylene chloride.

Coupling

In this formula"P"is amino protective group, as described previously,"A"is an active ester such as p-nitrophenyl, o-nitrophenyl or pentachlorophenyl, and"CA" is a coupling agent which is preferably dicyclohexylcarbodiimide (DCC), but may be any coupling agent which forms peptide bonds, such as diimides, azides or mixed anhydrides. The symbols (R), P, A and CA are to be taken as having the meanings above defined whenever they appear in the specification and claims.

Since the formula described previously begins to be cumbersome, it is best to rewrite the formula of the reaction product in the following manner: P-Asn-Phe-O-CH2- (R ? Wherein :"Phe"stands for phenylalanine residue,"Asn"stands for the asparagine residue and P and R are as previously defined. This simplified nomenclature will be utilized in the description of all subsequent reactions.

Deprotection, as explained in connection with the phenylalanine resin results in a product bearing the following formula : H-Asn-Phe-O-CH2- (R) (Compound No. 2) It is important that the coupling reaction be complete and it has been found that the Ninhydrin test, described by E. Kaiser, R. Colescott, C. D. Bossinger and P. Cook in Anal. Biochem. 34, 595-98 (1970), to be applicable to determine when the coupling reaction is sufficiently complete. If the Ninhydrin test is negative one proceed to the deprotection of the resm peptide and go on to the following coupling reaction.

If this test is positive the coupling step is repeated until the Ninhydrin test result is finally negative.

Following are specific examples of the coupling of asparagine: EXAMPLE 4 To a deprotected phenylalanine resin prepared according to Example 3 and having 3.5 meq of amine group was added a solution of 21 millimoles (approx. 300% excess) of BOC-L-asparagine in 40 ml of methylene chloride. After two minutes a solution of 21 meq of dicyclohexylcarbodiimide (DCC) was added and the mixture agitated for 45 minutes. The product was filtered and washed twice each with 40 ml portions of chloroform and methylene chloride. The Ninhydrin test was performed on a 3-5 mg sample of resin peptide reaction product and found to be negative. This resin was then deprotected as was described in Example 3.

EXAMPLE 5 Two grams of phenylalanine resin, deprotected and neutralized as described in Example 3, was washed three times with 25 ml of dimethyl formamide and shaken for 20 hours with 6 meq of BOC-L-asparagine p-nitrophenyl ester dissolved in 25 ml of dimethylformamide (DMF). The product was washed with two portions of dimethylformamide, two portions of methylene chloride, two portions of methanol and three portions of methylene chloride.

Synthesis of the Peptide The following Table 1 lists in sequence the amino acids attached at each of rections 2 to 34, indicating the position in the chain in which the attachment is made and listing the n actant used with the preferred protecting groups.

TABLE I Amino Acid Group Reaction Position Amino Acid With Preferred Number Number Being Attache Protectants 2 33 asparagine BOC-L-asparaginep nitrophenyi ester 3 32 histidine BOC-L-im-carbobenzyloxy- L-histidine 4 31 valine BOC-L-valine 5 30 asparatic acid BOC-L-beta-benzylaspartate 6 29 glutamine BOC-L-glutamine p-nitro phenyl ester 7 28 leucine BOC-L-leucine 8 27 lysine BRepsilon uoroacetyl L-lysine in 10% by volume DMF for solubility 9 26 lysine BOC-epsilon-trifluoroacetyl L-lysine in 10% by volume DMF for solubility 10 25 arginine BOC-L-tosylarginine in 20% by volume DMF for solubility 11 24 leucine BOC-L-leucine 12 23 tryptophane BOC-L-tryptophane in 10% by volume DMF for solubility 13 22 glutamic acid BOC-Lrgamma-benzyl- glutamate 14 21 valine BOC-L-valine 15 20 arginine BOC-L-tosylarginine in 20% DMF for solubility 16 19 glutamic acid BOC-L-gamma benzylglutamate 17 18 methionine BOC-L-methionine 18 17 serine BOC-O-benzyl-L-serine 19 16 asparagine BOC-L-asparagine psutroptenyl ester 20 15 leucine BtL-leucine 21 14 hisddine BOC-im-carbobenzyloxy- L-histidine 22 13 lysine BOC-epsilon-trifluoroacetyl L-lysine in 10% by volume DMF for solubility 23 12 glycine BOGglydne 24 11 leucine BOCUleucinc 25 10 asparagine BOC-L-asparagine p-nitrophenyl ester 26 9 histidine BOC-im-carbobenzyloxy L-histidine 27 8 methionine BOC-L-methionine 28 7 leucine BOC-L-leucine 29 6 glutamine BOC-L-glutamine p-nitrophenyl ester 30 5 isoleucine BOC-L-isoleucine TABLE 1 (Cont.) Amino Acid Group Reaction Position Amino Acid With Preferred Number Number Being Attached Protectants 31 4 glutamic acid BOC-Ia- benzylglutamate 32 3 serine BOC-0-benzyl- L-serine 33 2 valine BOC-L-valine 34 1 serine BOC-0-benzyl- L-serine As was described in connection with the attachment of asparagine in Reaction No. 2, (see Example 4), each succeeding reaction to attach another amino acid group involves the same procedure in which the resin peptide previously prepared is coupled with another protected amino acid derivative. The newly coupled peptide is then deprotected and neutralized. More specifically, the following steps may in the case of each reaction be as follows: Coupling : 7 millimoles of the appropriate BOC-amino acid (0. 43 equivalent excess in 40 ml of methylene chloride or DMF mixture where required).

7 millimoles of dicyclohexylcarbodiimide (coupling agent) in 15 ml of methylene chloride-45 minutes reaction time.

2 x 40 ml chloroform washes-2 minutes each.

2**40 ml**methylene chloride**2 minutes each.

Deprotection : 2 x 40ml-methylene chloride washes-2 minutes each 40 ml 50% by volume trifluoroacetic acid in methylene chloride-5 minutes (After Reaction No. 12, 1% by volume 2-mercaptoethanol or 1, 2-ethanedithiol is added to the 50% by volume trifluoroacetic acid in methylene chloride).

3X40 ml methylene chloride washes-2 minutes each.

2X40 mEmethand washes2 minutes each 3X40 ml chlorofotm washes2 minutes each.

Neutralization: 2x40 ml-10% by volume diisopropylamine in chloroform-5 minutes each.

4x40 ml-chloroform washes-2 minutes each.

The procedures for making the coupling, the deprotection and neutralization steps in each of rections 3 to 34 may be the same as already described in connection with reaction No. 2 except for the variations set forth in the following description.

As previously stated the Compound No. 2 which is the result of reaction No. 2 (after deprotection and neutralization) is: H-Asn-Phe-O-CHz- (R) and Compound No. 3, which is the result of reaction No. 3, is:

Compound No. 4, the result of reaction No. 4, is:

and, Compound No. 5, the result of reaction No. 5, is:

In reaction 3, at Position 32, where histidine is attached, I prefer to use carbo benzyloxy (CBZ) protection for the imidazole, but may use tosyl or dinitrophenyl (DNP) protection. The symbol"W'is defined to mean CBZ, Tosyl or DNP. In Reaction 5, at Position 30, where aspartic acid is attached I prefer to use benzyl or benzyl derivative protection. The symbol"Bz"is defined to mean benzyl, p-methoxy- benzyl, p-chlorobenzyl, p-nitrobenzyl or a benzhydryl group.

This pattern continues until the attachent of Gln at the 29th position. At this position the coupling agent DCC cannot be used unless the glutamine has a suitable protecting group, such as benzhydryl or xanthydryl, attached thereto or protecting catalysts are added to the solutions. Without such protection, DCC creates a side reaction which destroys some of the glutamine. Alternatively, glutamine can be coupled, when unprotected, as an"active ester"as in Example 5.

The deprotected resin peptide is agitated with an active ester of glutamine such as p-nitrophenyl ester, o-nitrophenyl ester or pentachlorophenyl ester.

This coupling is demonstrated more specifically by the following Example 6.

EXAMPLE 6 The resin peptide represented by Compound No. 5 obtained as a result of Reaction No. 5 (after deprotection and neutralization) was washed with three 40 ml portions of dimethylformamide for two minutes each. Twelve riihimoles of BOC-L glutamine-p-nitrophenyl ester dissolved in 40 ml of dimethylformamide was shaken with the resin for 20 hours, the resin was then washed with three portions of dimethyl formamide, three portions of methanol and three portions of methylene chloride. The glutamine at Position 6, Reaction 29, is attached in this same manner.

EXAMPLE 7 The asparagine at positions 16 and 10 as in position 33 are attached in the manner of Example 5 using BOC-L asparagine-p-nitrophenyl ester.

EXAMPLE 8 In place of the p-nitrophenyl ester of Examples 5, 6 and 7, either o-nitrophenyl ester or penta-chlorophenyl ester may be substituted, and the reaction carried out as set forth in Examples 5,6 and 7 to accomplish the coupling of glutamine and asparagine.

The coupling at position 27 is followed by the usual deprotection and neutraliza- tion and results in a resin peptide compound No. 8 and is represented by the following formula:

(Compound 8) Where lysine (Lys) is attached, it is preferred to use triSuoroacetyl as the epsilon amine protecting agent.

It is believed that this resin peptide was made for the first time by the present invention and that this is an important link in the synthesis of the hormone, HPTH fragment.

The coupling at position 16 is followed by the usual deprotection and neutralization and this results in a resin peptide compound No. 19 and is represented by the following formula:

(Compound 19) For the coupling of the arginine amino acid in Reaction No. 10, at Position No.

Z5, 1 prefer to use as the guanidine protection agent the tosyl group (p-toluene sulfonyl), but may use a nitro group, and in the formula of this specification we employ the symbol"T"to mean tosyl or nitro.

The symbol T has the meaning as above throughout this specification and claims.

After each coupling reaction, and before deprotection of the resin peptide, the Ninhydrin test is applied. If the test is"positive"the coupling reaction last performed is repeated. If the test is"negative", one may proceed to the deprotection of the resin peptide.

Upon the attachment of serine in Reacion 34, at the number one position, according to the manner and sequence above described, and after the deprotection and neutralization of the coupled resin peptide, I arrive at Compound No. 34 which has the following formula:

(Compound 34) This resin peptide is then treated to remove the resin and protecting groups.

Suitably, the resin and most of the remaining protective groups may be removed by treatment with anhydrous hydrogen fluoride. The formula for this reaction is:

(Reaction 35)

(Compound 35) The following Example 9 illustrates the cleavage reaction.

EXAMPLE 9 Two grams of the blocked HPTH resin peptide were placed in a Kel-F vessel with 2 ml of anisole and 10 mls of anhydrous hydrogen fluoride was added by distillation. This mixture was stirred at 0 C for 1 hour. The hydrogen fluoride was removed by vacuum distillation, the residue washed 4 times with ethyl acetate followed by extraction with glacial acetic acid. The acetic acid extract was lyophilized to give 779 mg of a fluffy white powder. This process removes the peptide from the resin and removes all blocking groups on the difunctional amino acids except the trifluoro acetyl (TFA) blocking group of the lysine residues. Hence, this product is called TFA-HPTH peptide, (Compound 35).

Compound 35 can be treated with an aqueous base such as 1 molar piperidine or 2N ammonium hydroxide which removes the TFA lysine protecting groups to generate 1-34 HPTH fragment compound No. 36 which has the following formula: H-Ser-Val-Ser-Glu-Ile-Gln-Leu-Met-His-Asn-Leu-Gly-Lys-His-Leu-Asn-Ser-Met- 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Glu-Arg-Val-Glu-Trp-Leu-Arg-Lys-Lys-Leu-Gln-Asp-Val-His-Asn-Phe-OH 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 (Compound 36) EXAMPLE 10 In the same manner as described in the previous examples, a 1-34 resin peptide was prepared in which the No. 1 L-serine was replaced by D-serine by treating Compound 33 with BOC-O-benzyl-D-serine (instead of BOCO-benzyl-L-serine). After removal of the resin and all of the remaining protecting groups, the formula of the reaction product is: H-D-Ser-Val-Ser-Glu-Ile-Gln-Leu-Met-His-Asn-Leu-Gly-Lys-His-Leu-Asn-Ser-Met- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Glu-Arg-Val-Glu-Trp-Leu-Arg-Lys-Lys-Leu-Gln-Asp-Val-His-Asn-Phe-OH 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 (Compound 37) This analog has biological activity when tested in the Chick Hypercalcemia assay: J. A. Parsons, B. Reit and C. J. Robinson, Endocrinology, 92,454 (1973).

Purification After gel filtration on Biogel P-6, (Biorad-Registered Trade Mark) the crude 1 to 34 human parathyroid hormone peptide [HPTH (1-34)] was chromatographed on carboxymethylcellulose (CMC) (Whatman CM52 the word"Whatman"is a Registered Trade Mark) using a linear gradient of ammonium acetate buffer. After desalting on polyacrylamide gel, the homogeneity of the synthetic peptides was checked by thin-layer chromatography on cellulose (Brinkmann Celplate-22, Eastman 6065) and silica gel (Merck-Registered Trade Mark). plates. The sample load was 30ug in 5 ul of 0. 1M acetic acid. The following solvent systems were used: Rra, n-butanol/acetic acid/water 4: 1: 5 (v/v); Rr', ethyl acetate/pyridine/acetic acid/water 5: 5 : 1: 3 (v/v); Rro, n-butanol/pyridine/acetic acid/water 15: 10: 3: 12 (v/v); R, d, n-butanol/acetic acid/water/ethyl acetate 1: 1: 1: 1 (v/v). The peptide spots were visualized by spraying the plates with Ehrlich reagent and 0.5% by volume; ninhydrin in ethanol. The purified synthetic HPTH (1-34) peptide gave a single spot with Ra (cellulose, Brinkman) 0.19; R (I (silica) 0.11; Rfe (silica) 0. 17 ; Roc (cellulose, Brinkman) 0.40; Rfc (cellulose, Eastman 6065) 0.66; and R d (cellulose, Brinkman) 0.48.

The biological activities of the synthetic HPTH (1-34) peptide in the in vitro Rat Kidney Adenylate Cyclase assay and the Chick Hypercalcemia Assay are shown in the following Table 2. Included for comparison are the corresponding data on the native bovine (1-84) [BPTH (1-84) (native)] and the synthetic bovine (1-34) [BPTH (1-34)] peptides, as well as the native Human PTH (1-84).

TABLE 2 Biological Activity of Synthetic and Native Parathyroid Hormones In vitro In vivo Rat Kidney Chick Adenylate Cyclase Hypercalcemia [MRC* u/mg] [MRC* u/mg] HPTH (1-84) (native) 350 Unknown HPTH (1-34) (purifie Compound 36) 3600 3200 BPTH (1-84) (native) 3000 2500 BPTH (1-34) 5400 7700 * Medical Reseanch Council of England.

Claims (17)

WHAT WE CLAIM IS :-

1. A resin peptide containing the structure

wherein: (R) is an insoluble polystyrene resin ; W is a carbobenzyloxy, tosyl or 2,4-dinitrophenyl group ; Bz is a benzyl, p-methoxybenzyl, p-chlorobenzyl, p-nitrobenzyl or benzhydryl group; and TFA is a trifluoroacetyl group.

2. A resin peptide as claimed in claim 1 of the formula

wherein: (R), W, Bz and TFA are as defined in claim 1.

3. A resin peptide as claimed in claim 1 of the formula

wherein: (R), W, Bz and TFA are as defined in claim 1, and T is a tosyl or nitro group.

4. A synthetic peptide containing the structure : -Lys-Leu-Gln-Asp-Val-His-Asn-Phe-

5. A synthetic peptide as claimed in claim 4 of the formula

Val-His-Asn-Phe-OH wherein : TFA is a trifluoroacetyl group.

6. A synthetic peptide as claimed in claim 4 of the formula:

Gln-Asp-Val-His-Asn-Phe-OH wherein: TFA is a trifluoroacetyl group.

7. A process for synthesizing a resin peptide which comprises coupling,

to produce a resin peptide having the structure:

wherein: (R), W, Bz and TFA are as defined in claim 1 and P is an amine protecting group selected from tertiary-butyloxycarbonyl, amyloxycarbonyl, and o-nitrophenyl- sulphenyl.

8. A process as claimed in claim 7, including the additional step of removing P from the structure.

9. A process as claimed in claim 8 including the additional step of coupling

to the reaction product of claim 8 to produce a resin peptide having the structure :

wherein: (R), W, Bz, TFA and P are as defined in claim 7.

10. A process for synthesizing a resin peptide which comprises coupling B*Ser (Bz)-OH or P-D-Ser (Bz)-OH to

to produce a resin peptide having the structure :-

respectively, wherein (R), W, Bz and TFA are as defined in Claim 1, P is as defined in Claim 7 and T is a tosyl or nitro group.

11. A process as claimed in Claim 10, which further comprises removing P from the structure obtained.

12. A process as claimed in Claim 11 which further comprises contacting the reaction product of Claim 11 with anhydrous hydrogen fluoride to remove the (R) CH2, Bz, T and W groups and to produce a synthetic peptide as claimed in Claim 5 or Claim 6.

13. A process as claimed in Claim 12 which further comprises contacting the reaction product of Claim 12 with an aqueous base to remove the TFA group therefrom.

14. A resin peptide as claimed in Claim 1 substantially as described with reference to any one of the Examples.

15. A synthetic peptide as claimed in Claim 4 substantially as described with reference to Example 9 or 10.

16. A process as claimed in Claim 8 substantially as described with reference to Example 8.

17. A process as claimed in Claim 11, substantially as described with reference to Example 8.