Synthesis of dolastatin 3
First Claim
Patent Images
1. A process for synthesizing a peptide having the structure cyclo comprising the steps of adding triethylamine and diethyl phosphorocyanidate to S-proline methyl ester and N-t-Boc-L-valine in 1,2-dimethoxyethane at 0°
- C. to form a dipeptide;
holding said depeptide at 0°
C. for one hour;
allowing said dipeptide to warm to room temperature over a period of 4 hours;
diluting the warmed depeptide with ethyl acetate to form a diluted mixture;
washing said diluted mixture first with 5% HCl;
then with sodium hydrogen carbonate and finally with saturated brine and removing the solvent therefrom in vacuo to provide N-t-Boc-L-Val-L-Pro-OMe as a colorless syrup;
stirring said colorless syrup into a solution of dry dichloromethane at 0°
C.;
adding trifluoroacetic acid to said syrup mixture and holding said syrup mixture at 0°
C. for one hour;
warming said cold syrup-mixture to room temperature;
holding said syrup-mixture at room temperature for one hour;
diluting said warmed syrup mixture with dry carbon tetrachloride;
removing the solvents from said diluted syrup mixture in vacuo to provide a colorless syrup residue;
drying said colorless syrup residue under vacuum for twelve hours to provide a dipeptide trifluoroacetate;
mixing said dipeptide trifluoroacetate and N-t-Boc-(gly)Thz in dry dimethoxyethane to form a solution;
cooling said solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said cooled solution 0°
C. for one hour;
warming said cooled solution to room temperature over four hours to for a warmed solution;
diluting said warmed solution with ethyl acetate;
washing said diluted warmed solution with 5% HCl and sodium hydrogen carbonate;
further washing the washed diluted warmed solution with saturated brine;
drying said further washed warmed solution with sodium sulfate;
removing the solvent from said solution in vacuo to provide a residue of N-t-Boc-(gly)Thz-L-Val-L-Pro-OMe as a colorless syrup;
placing said residue of N-t-Boc-(gly)Thz-L-Val-L-Pro-OMe in dry dichloromethane at 0°
C.;
adding trifluoroacetic acid to said residue and said dry dichloromethane to form a mixture;
holding said mixture at 0°
C. for one hour;
warming said last formed mixture to room temperature for one hour;
diluting said room temperature mixture with carbon tetrachloride;
removing the solvents from said diluted mixture in vacuo to leave a tripeptide trifluoroacetate as a colorless syrup;
drying said colorless syrup under vacuum for 24 hours;
dissolving said dried syrup in dry dimethylformamide to form a tripeptide trifluoroacetate/dimethylformamide solution;
adding N-t-Boc-(gly)Thz to said tripeptide trifluoroacetate/dimethylformamide solution;
cooling said solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said solution at 0°
C. for one hour;
warming said cool solution to room temperature for six hours;
removing the solvents from said warmed solution in vacuo to provide a residue of protected tetrapeptide N-t-Boc-(gly)Thz-(gly)Thz-L-Val-L-Pro-OMe;
dissolving said protected tetrapeptide in trifluoroacetic acid at 0°
C.;
warming said solution to room temperature;
diluting said solution with carbon tetrachloride;
removing said solvents in vacuo to leave a tetrapeptide trifluoroacetate as a residue;
drying said residue under vacuum for 24 hours;
dissolving said dried residue in dimethylformamide to form a dimethylformamide solution;
adding N-t-Boc-L-Leu to said dimethylformamide solution;
cooling the resulting solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said cooled solution at 0°
C. for one hour;
warming said cooled solution to room temperature for four hours;
removing the solvents from said room temperature solution in vacuo to leave a residue;
purifying said residue on a silica column in 7% methanol and ethyl acetate to produce a protected pentapeptide N-t-Boc-L-Leu-L-(gln)Thz-(gly)Thz-L-Val-L-Pro-OMe;
placing the protected pentapeptide in dioxane and water;
treating the dioxane/water solution with sodium hydroxide at room temperature for three hours;
diluting the treated solution with diethyl ether to form a diluted treated solution having an aqueous phase;
collecting the aqueous phase of said diluted treated solution;
adjusting the pH of said aqueous phase to 2 with all cold 2N HCl;
extracting said pH adjusted aqueous phase with chloroform to create a plurality of extracts;
combining said extracts;
drying said combined extracts with anhydrous sodium sulfate;
removing the solvent from said dried extracts in vacuo leaving an N-Boc-pentapeptide;
precipitating N-Boc-pentapeptide from ethanol with diethyl ether;
placing the N-Boc-pentapeptide precipitate in dry dimethoxyethane and dimethylformamide to form a solution;
treating said solution with pentafluorophenol and N,N1 -dicyclohexyl-carbodiimide at -20°
C. in a nitrogen atmosphere;
warming said treated solution to room temperature;
holding said warmed solution at room temperature for 12 hours;
filtering said warmed solution to remove dicyclohexylurea therefrom;
removing the solvents from said filtered warmed solution in vacuo to leave a pentapeptide pentafluorophenyl ester;
treating said pentapeptide pentafluorophenyl ester with trifluoroacetic acid at room temperature to form a reaction mixture;
diluting said reaction mixture with carbon tetrachloride;
removing the solvents from said diluted reaction mixture in vacuo to leave a pentapeptide trifluoroacetate ester as the residue;
drying said residue under vacuum;
dissolving said dried residue in dioxane to produce a solution of 4-pyrrolidinopyridine in t-butanol and dioxane at 95°
C.;
filtering said solution through celite to create a residue; and
removing the solvent from said residue in vacuo to produce Cyclo-[L-Val-L-Pro-L-Leu-L(gln)Thz-(gly)Thz] as an amorphous white powder.
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Abstract
Synthesis of dolastatin 3 is accomplished by one amino acid unit addition from L-Pro-OMe employing diethyl phosphorocyanidate-triethylamine for peptide bond formation and N-Boc protection (trifluoroacetic acid cleavage). Thereafter Boc-L-Leu-L-(gln)Thz-(gly)Thz-L-Val-L-Pro-OMe was obtained, successively crystallized from ethanol-diethyl ether, converted to the OPfp active ester, Boc cleavage and cyclization in dioxane containing t-butanol and 4-pyrrolidinopyridine to yield synthetic (-)-dolastatin 3.
28 Citations
21 Claims
-
1. A process for synthesizing a peptide having the structure cyclo comprising the steps of adding triethylamine and diethyl phosphorocyanidate to S-proline methyl ester and N-t-Boc-L-valine in 1,2-dimethoxyethane at 0°
- C. to form a dipeptide;
holding said depeptide at 0°
C. for one hour;
allowing said dipeptide to warm to room temperature over a period of 4 hours;
diluting the warmed depeptide with ethyl acetate to form a diluted mixture;
washing said diluted mixture first with 5% HCl;
then with sodium hydrogen carbonate and finally with saturated brine and removing the solvent therefrom in vacuo to provide N-t-Boc-L-Val-L-Pro-OMe as a colorless syrup;
stirring said colorless syrup into a solution of dry dichloromethane at 0°
C.;
adding trifluoroacetic acid to said syrup mixture and holding said syrup mixture at 0°
C. for one hour;
warming said cold syrup-mixture to room temperature;
holding said syrup-mixture at room temperature for one hour;
diluting said warmed syrup mixture with dry carbon tetrachloride;
removing the solvents from said diluted syrup mixture in vacuo to provide a colorless syrup residue;
drying said colorless syrup residue under vacuum for twelve hours to provide a dipeptide trifluoroacetate;
mixing said dipeptide trifluoroacetate and N-t-Boc-(gly)Thz in dry dimethoxyethane to form a solution;
cooling said solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said cooled solution 0°
C. for one hour;
warming said cooled solution to room temperature over four hours to for a warmed solution;
diluting said warmed solution with ethyl acetate;
washing said diluted warmed solution with 5% HCl and sodium hydrogen carbonate;
further washing the washed diluted warmed solution with saturated brine;
drying said further washed warmed solution with sodium sulfate;
removing the solvent from said solution in vacuo to provide a residue of N-t-Boc-(gly)Thz-L-Val-L-Pro-OMe as a colorless syrup;
placing said residue of N-t-Boc-(gly)Thz-L-Val-L-Pro-OMe in dry dichloromethane at 0°
C.;
adding trifluoroacetic acid to said residue and said dry dichloromethane to form a mixture;
holding said mixture at 0°
C. for one hour;
warming said last formed mixture to room temperature for one hour;
diluting said room temperature mixture with carbon tetrachloride;
removing the solvents from said diluted mixture in vacuo to leave a tripeptide trifluoroacetate as a colorless syrup;
drying said colorless syrup under vacuum for 24 hours;
dissolving said dried syrup in dry dimethylformamide to form a tripeptide trifluoroacetate/dimethylformamide solution;
adding N-t-Boc-(gly)Thz to said tripeptide trifluoroacetate/dimethylformamide solution;
cooling said solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said solution at 0°
C. for one hour;
warming said cool solution to room temperature for six hours;
removing the solvents from said warmed solution in vacuo to provide a residue of protected tetrapeptide N-t-Boc-(gly)Thz-(gly)Thz-L-Val-L-Pro-OMe;
dissolving said protected tetrapeptide in trifluoroacetic acid at 0°
C.;
warming said solution to room temperature;
diluting said solution with carbon tetrachloride;
removing said solvents in vacuo to leave a tetrapeptide trifluoroacetate as a residue;
drying said residue under vacuum for 24 hours;
dissolving said dried residue in dimethylformamide to form a dimethylformamide solution;
adding N-t-Boc-L-Leu to said dimethylformamide solution;
cooling the resulting solution to 0°
C.;
adding triethylamine and DEPC to said cooled solution;
holding said cooled solution at 0°
C. for one hour;
warming said cooled solution to room temperature for four hours;
removing the solvents from said room temperature solution in vacuo to leave a residue;
purifying said residue on a silica column in 7% methanol and ethyl acetate to produce a protected pentapeptide N-t-Boc-L-Leu-L-(gln)Thz-(gly)Thz-L-Val-L-Pro-OMe;
placing the protected pentapeptide in dioxane and water;
treating the dioxane/water solution with sodium hydroxide at room temperature for three hours;
diluting the treated solution with diethyl ether to form a diluted treated solution having an aqueous phase;
collecting the aqueous phase of said diluted treated solution;
adjusting the pH of said aqueous phase to 2 with all cold 2N HCl;
extracting said pH adjusted aqueous phase with chloroform to create a plurality of extracts;
combining said extracts;
drying said combined extracts with anhydrous sodium sulfate;
removing the solvent from said dried extracts in vacuo leaving an N-Boc-pentapeptide;
precipitating N-Boc-pentapeptide from ethanol with diethyl ether;
placing the N-Boc-pentapeptide precipitate in dry dimethoxyethane and dimethylformamide to form a solution;
treating said solution with pentafluorophenol and N,N1 -dicyclohexyl-carbodiimide at -20°
C. in a nitrogen atmosphere;
warming said treated solution to room temperature;
holding said warmed solution at room temperature for 12 hours;
filtering said warmed solution to remove dicyclohexylurea therefrom;
removing the solvents from said filtered warmed solution in vacuo to leave a pentapeptide pentafluorophenyl ester;
treating said pentapeptide pentafluorophenyl ester with trifluoroacetic acid at room temperature to form a reaction mixture;
diluting said reaction mixture with carbon tetrachloride;
removing the solvents from said diluted reaction mixture in vacuo to leave a pentapeptide trifluoroacetate ester as the residue;
drying said residue under vacuum;
dissolving said dried residue in dioxane to produce a solution of 4-pyrrolidinopyridine in t-butanol and dioxane at 95°
C.;
filtering said solution through celite to create a residue; and
removing the solvent from said residue in vacuo to produce Cyclo-[L-Val-L-Pro-L-Leu-L(gln)Thz-(gly)Thz] as an amorphous white powder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
- C. to form a dipeptide;
Specification