Thermally Sensitive Protecting Groups for Cysteine, and Manufacture and Use Thereof

Abstract

In a preferred embodiment, there is provided a protecting group for protecting the thiol side chain of a cysteine residue, the protecting group comprising a Diels-Alder cycloadduct of a furan and a maleimide, and optionally, a linker interposed between the thiol side chain and the Diels-Alder cycloadduct.

We claim: 
     
         1 . A protecting group for protecting a cysteine residue, the protecting group having structural formula 1 or 2: 
       
         
           
           
               
               
           
         
       
       wherein
 R is an electron withdrawing group or a leaving group; 
 X and Y are independently of each other oxygen, sulfur, nitrogen or phosphorus; 
 R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, heteroaralkyl, formyl, haloformyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, (alkoxycarbonyl)oxy, carbamoyl, amino, amido, imino, imido, azo, cyanato, isocyanato, cyano, nitro, sulfanyl, thiocyanato or phosphono, each of which is optionally substituted; and n is an integer between 1 and 12, inclusive. 
 
     
     
         2 . The protecting group of  claim 1 , wherein R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, formyl, carbonyl, carboxyl, alkoxy, amino or nitro, each of which is optionally substituted. 
     
     
         3 . The protecting group of  claim 1 , wherein R 1  is hydrogen, hydroxyl, halo, alkyl, formyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, amino or nitro, each of which is optionally substituted, and R 2  is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl, each of which is optionally substituted. 
     
     
         4 . The protecting group of  claim 1 , wherein R 1  is hydrogen, nitro, halo or alkoxy, and R 2  is alkyl, aryl or heteroaryl, each of which is optionally substituted, or wherein R 1  is hydrogen, nitro, bromo, chloro, fluoro, methoxy or ethoxy, and R 2  is methyl, ethyl, propyl, butyl, phenyl, p-methoxyphenyl, p-nitrophenyl or benzyl. 
     
     
         5 . The protecting group of  claim 1 , wherein X and Y are independently of each other oxygen or nitrogen, or wherein X is nitrogen and Y is oxygen. 
     
     
         6 . The protecting group of  claim 1 , wherein n is an integer between 1 and 4, inclusive. 
     
     
         7 . The protecting group of  claim 1 , wherein R is hydroxyl, alkyl, alkenyl or halo, or wherein R is hydroxyl, chloro, methyl or allyl. 
     
     
         8 . A protected cysteine having structural formula 9 or 10: 
       
         
           
           
               
               
           
         
       
       wherein
 X and Y are independently of each other oxygen, sulfur, nitrogen or phosphorus; 
 R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, heteroaralkyl, formyl, haloformyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, (alkoxycarbonyl)oxy, carbamoyl, amino, amido, imino, imido, azo, cyanato, isocyanato, cyano, nitro, sulfanyl, thiocyanato or phosphono, each of which is optionally substituted; 
 R 3  and R 4  are independently each other hydrogen or a protecting group; and 
 n is an integer between 1 and 12, inclusive. 
 
     
     
         9 . The protected cysteine of  claim 8 , wherein R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, formyl, carbonyl, carboxyl, alkoxy, amino or nitro, each of which is optionally substituted. 
     
     
         10 . The protected cysteine of  claim 8 , wherein R 1  is hydrogen, hydroxyl, halo, alkyl, formyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, amino or nitro, each of which is optionally substituted, and R 2  is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl, each of which is optionally substituted. 
     
     
         11 . The protected cysteine of  claim 8 , wherein R 1  is hydrogen, nitro, halo or alkoxy, and R 2  is alkyl, aryl or heteroaryl, each of which is optionally substituted or wherein R 1  is hydrogen, nitro, bromo, chloro, fluoro, methoxy or ethoxy, and R 2  is methyl, ethyl, propyl, butyl, phenyl, p-methoxyphenyl, p-nitrophenyl or benzyl. 
     
     
         12 . The protected cysteine of  claim 8 , wherein X and Y are independently of each other oxygen or nitrogen or wherein X is nitrogen and Y is oxygen. 
     
     
         13 . The protected cysteine of  claim 8 , wherein n is an integer between 1 and 4, inclusive. 
     
     
         14 . The protected cysteine of  claim 8 , wherein R 3  and R 4  are independently each other hydrogen, alkyl, allyl, tert-Butyloxycarbonyl (Boc), fluorenylmethyloxycarbonyl (Fmoc), tert-butyldimethylsilyl (TBS), methoxymethyl (MOM), ethoxymethyl (EOM), p-methoxybenzyl or p-nitrobenzyl or wherein R 3  is hydrogen or allyand R 4  is Fmoc. 
     
     
         15 . A compound having structural formula 1 or 2: 
       
         
           
           
               
               
           
         
       
       wherein
 R is an electron withdrawing group or a leaving group; 
 X and Y are independently of each other oxygen, sulfur, nitrogen or phosphorus; 
 R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, heteroaralkyl, formyl, haloformyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, (alkoxycarbonyl)oxy, carbamoyl, amino, amido, imino, imido, azo, cyanato, isocyanato, cyano, nitro, sulfanyl, thiocyanato or phosphono, each of which is optionally substituted; and 
 n is an integer between 1 and 12, inclusive. 
 
     
     
         16 . The compound of  claim 15 , wherein R 1  and R 2  are independently of each other hydrogen, hydroxyl, halo, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, formyl, carbonyl, carboxyl, alkoxy, amino or nitro, each of which is optionally substituted. 
     
     
         17 . The compound of  claim 15 , wherein R 1  is hydrogen, hydroxyl, halo, alkyl, formyl, carbonyl, carboxyl, alkoxy, alkoxycarbonyl, amino or nitro, each of which is optionally substituted, and R 2  is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl, each of which is optionally substituted. 
     
     
         18 . The compound of  claim 15 , wherein R 1  is hydrogen, nitro, halo or alkoxy, and R 2  is alkyl, aryl or heteroaryl, each of which is optionally substituted or wherein R 1  is hydrogen, nitro, bromo, chloro, fluoro, methoxy or ethoxy, and R 2  is methyl, ethyl, propyl, butyl, phenyl, p-methoxyphenyl, p-nitrophenyl or benzyl. 
     
     
         19 . The compound of  claim 15 , wherein X and Y are independently of each other oxygen or nitrogen or wherein X is nitrogen and Y is oxygen. 
     
     
         20 . The compound of  claim 15 , wherein n is an integer between 1 and 4, inclusive. 
     
     
         21 . The compound of  claim 15 , wherein R is hydroxyl, alkyl, alkenyl or halo or wherein R is hydroxyl, chloro, methyl or allyl.