One pot synthesis of taxane derivatives and their conversion to paclitaxel and docetaxel

Abstract

A process is provided for the semi-synthesis of taxane intermediates useful in the preparation of paclitaxel and docetaxel, in particular, the semi-synthesis of protected taxane intermediate in a one pot reaction of protecting the C-7, 10 and attaching a side chain at C-13 position and subsequently deprotecting the group to form paclitaxel or docetaxel, and intermediates used therein.

1 . A process for protecting a taxane of Formula (I):  
       
         
           
           
               
               
           
         
       
       wherein, Z is —OH or a protected —OH, G 1  and G 2  are the same or different and independently a hydroxy protecting group, the process comprising: 
 protecting the free hydroxy groups at the C-7 position and/or the C-10 position of the taxane; and  
 attaching a side chain to the free hydroxy group at the C-13 position of the taxane to provide a C-13 protected taxane intermediate,  
 wherein the steps of protecting and attaching comprises, in a one-pot reaction, combining the taxane with a base, a suitable hydroxy protecting agent and a precursor to the side chain, and wherein the precursor to the side chain is a beta-lactam, oxazolidine or oxazoline.  
 
     
     
         2 . The process of  claim 1  wherein the precursor to the side chain is a beta-lactam of formula (II):  
       
         
           
           
               
               
           
         
       
       wherein, 
 R 1  is a hydroxy group, protected hydroxy group, thiol group or protected thiol group;  
 R 2  is alkyl, alkenyl, alkynyl or aryl; and  
 R 3  is hydrogen, C 1 -C 6  alkyl, aryl or acyl.  
 
     
     
         3 . The process of  claim 2  wherein the beta-lactam has the structure:  
       
         
           
           
               
               
           
         
       
     
     
         4 . The process of  claim 1  wherein Z is —OH or —OAc.  
     
     
         5 . The process of  claim 1  wherein G 1  is benzoyl and G 2  is acetyl.  
     
     
         6 . The process of  claim 5  wherein the compound of Formula (I) is 10-deacetylbaccatin III or baccatin III.  
     
     
         7 . The process of  claim 1  wherein the base is DMAP, pyridine, TEA, LiOH, Li-t-OBu, n-BuLi, LiH, LiHMDS, KHMDS, K-t-OBu, NaH, NaHMDS or a mixture of any two or more of the foregoing.  
     
     
         8 . The process of  claim 1  wherein the combined steps of protecting and attaching in a one pot reaction further comprises combining the taxane of Formula (I) with a metal alkoxide, wherein the metal is selected from the group consisting of Group I, II and III metals and transition metals.  
     
     
         9 . The process of  claim 8  wherein the metal is lithium, sodium or potassium.  
     
     
         10 . The process of  claim 1  wherein the hydroxy protecting agent is an alkylating agent, a silylating agent or an acylating agent.  
     
     
         11 . The process of  claim 10  wherein the hydroxy-protecting group is tert-butoxycarbonyl (t-BOC), benzyloxycarbonyl (CBZ), 2,2,2-trichloroethoxycarbonyl (Troc), 9-fluorenyl methoxycarbonyl (Fmoc), 2,2,2-trichloroethoxymethyl, trimethyl silyl, triethyl silyl, dimethyl(t-butyl) silyl, diethylmethylsilyl, dimethyl phenylsilyl, diphenylmethylsilyl, acetyl, chloroacetyl, dichloroacetyl trichloroacetyl or trifluoroacetyl.  
     
     
         12 . The process of  claim 11  wherein the base is DMAP or n-BuLi and the hydroxy-protecting agent is tert-butoxycarbonyl or dichloroacetyl.  
     
     
         13 . The process of  claim 1  wherein the taxane of Formula (I) is part of a mixture of taxanes comprising a taxane of Formula (I), paclitaxel, 9-dihydro-13-acetylbaccatin III, cephalomannine, 10-deacetyl taxol, 7-xylosyl taxol and 10-deacetyl-7-xylosyl taxol.  
     
     
         14 . A process for preparing paclitaxel or docetaxel, comprising: 
 (1) protecting the hydroxy group at the C-7 and/or C-10 position of a compound of formula (V):                          wherein, Z is —OH or protected —OH,    (2) attaching a side chain to the free hydroxyl group at C-13 position to provide a C-13 protected taxane intermediate; and    (3) converting the C-13 protected taxane intermediate to paclitaxel or docetaxel,    wherein the steps of protecting and attaching comprise, combining in a one pot reaction, the compound of Formula (V) with a base, a suitable hydroxy protecting agent and a precursor to the side chain, and wherein the precursor to the side chain is a beta-lactam, oxazolidine or oxazoline.    
     
     
         15 . The process of  claim 14  wherein the compound of Formula (V) is 10-deacetylbaccatin III or baccatin III.  
     
     
         16 . The process of  claim 14  wherein the precursor to the side chain is a beta-lactam of formula (II):  
       
         
           
           
               
               
           
         
       
       wherein, 
 R 1  is a hydroxy group, protected hydroxy group, thiol group or protected thiol group;  
 R 2  is alkyl, alkenyl, alkynyl or aryl; and  
 R 3  is hydrogen, C 1 -C 6  alkyl, aryl or acyl.  
 
     
     
         17 . The process of  claim 16  wherein the beta-lactam has the structure:  
       
         
           
           
               
               
           
         
       
     
     
         18 . The process of  claim 14  wherein the base is DMAP, pyridine, TEA, LiOH, Li-t-OBu, n-BuLi, LiH, LiHMDS, KHMDS, K-t-OBu, NaH, NaHMDS or a mixture of any two or more of the foregoing.  
     
     
         19 . The process of  claim 14  wherein the hydroxy protecting agent is an alkylating agent, a silylating agent or an acylating agent.  
     
     
         20 . The process of  claim 19  wherein the hydroxy-protecting group is tert-butoxycarbonyl (t-BOC), benzyloxycarbonyl (CBZ), 2,2,2-trichloroethoxycarbonyl (Troc), 9-fluorenyl methoxycarbonyl (Fmoc), 2,2,2-trichloroethoxymethyl, trimethyl silyl, triethyl silyl, dimethyl(t-butyl) silyl, diethylmethylsilyl, dimethyl phenylsilyl, diphenylmethylsilyl, acetyl, chloroacetyl, dichloroacetyl trichloroacetyl or trifluoroacetyl.  
     
     
         21 . A process for preparing paclitaxel or docetaxel from an initial mixture of taxanes comprising 10-deacetylbaccatin III and at least one additional taxane selected from paclitaxel, 9-dihydro-13-acetylbaccatin III, baccatin III, cephalomannine, 10-deacetyl taxol, 7-xylosyl taxol and 10-deacetyl-7-xylosyl taxol, the process comprising: 
 (1) protecting the hydroxy group at the C-7 position of each taxane in the initial mixture having a hydroxy group at the C-7 position to yield a first intermediate mixture of C-7 protected taxanes;    (2) attaching a side chain to the C-13 position of each taxane having a free hydroxy group at the C-13 position in the first intermediate mixture to provide a mixture of C-13 protected taxane intermediates; and    (3) converting the C-13 protected taxane intermediates to paclitaxel or docetaxel,    wherein the steps of protecting the C-7 hydroxy groups and attaching a side chain to the free hydroxyl at the C-13 position comprises: combining, in a one pot reaction, the initial mixture with a base, a suitable hydroxy protecting agent and a precursor to the side chain, and wherein the precursor to the side chain is a beta-lactam, oxazolidine or oxazoline.    
     
     
         22 . The process of  claim 21  wherein the precursor to the side chain is a beta-lactam of Formula (II):  
       
         
           
           
               
               
           
         
       
       wherein, 
 R 1  is a hydroxy group, protected hydroxy group, thiol group or protected thiol group;  
 R 2  is alkyl, alkenyl, alkynyl or aryl; and  
 R 3  is hydrogen, C 1 -C 6  alkyl, aryl or acyl.  
 
     
     
         23 . The process of  claim 22  wherein the beta-lactam has the structure:  
       
         
           
           
               
               
           
         
       
     
     
         24 . The process of  claim 21  wherein the step of protecting the hydroxy group at the C-7 position of each taxane in the initial mixture further comprises protecting a free hydroxy group at the C-10 position of each taxane in the initial mixture having a hydroxy group at the C-10 position.  
     
     
         25 . The process of  claim 21  wherein the initial mixture comprises 10-deacetylbaccatin III and at least two additional taxanes selected from paclitaxel, 9-dihydro-13-acetylbaccatin III, baccatin III, cephalomannine, 10-deacetyl taxol, 7-xylosyl taxol and 10-deacetyl-7-xylosyl taxol.  
     
     
         26 . The process of  claim 21  wherein the initial mixture comprises 10-deacetylbaccatin III and at least three additional taxanes selected from paclitaxel, 9-dihydro-13-acetylbaccatin III, baccatin III, cephalomannine, 10-deacetyl taxol, 7-xylosyl taxol and 10-deacetyl-7-xylosyl taxol.  
     
     
         27 . The process of  claim 21  wherein the initial mixture comprises 10-deacetylbaccatin III, paclitaxel, 9-dihydro-13-acetylbaccatin III, baccatin III, cephalomannine, 10-deacetyl taxol, 7-xylosyl taxol and 10-deacetyl-7-xylosyl taxol.  
     
     
         28 . The process of  claim 21  wherein the initial mixture of taxanes is a waste taxane solution comprising one or more of the following: 
 pooled waste stream fractions collected during a chromatographic separation of a crude or partially purified taxane extract; and    pooled waste mother liquors collected during a recrystallization of a crude or partially purified taxane extract.    
     
     
         29 . The process of  claim 28  wherein the waste taxane solution comprises pooled waste stream fractions collected during a chromatographic separation of a crude taxane extract.  
     
     
         30 . The process of  claim 28  wherein the waste taxane solution comprises pooled waste stream fractions collected during chromatographic separations of both crude and partially purified taxane extracts and pooled waste mother liquors collected during recrystallizations of both crude and partially purified taxane extracts.  
     
     
         31 . The process of  claim 28  wherein the crude and partially purified taxane extracts are obtained from taxane-containing materials from the genus  Taxus.    
     
     
         32 . The process of  claim 21  wherein the base is DMAP, pyridine, TEA, LiOH, Li-t-OBu, n-BuLi, LiH, LiHMDS, KHMDS, K-t-OBu, NaH, NaHMDS or a mixture of any two or more of the foregoing.  
     
     
         33 . The process of  claim 21  wherein the hydroxy protecting agent is an alkylating agent, a silylating agent or an acylating agent.  
     
     
         34 . The process of  claim 33  wherein the hydroxy-protecting group is tert-butoxycarbonyl (t-BOC), benzyloxycarbonyl (CBZ), 2,2,2-trichloroethoxycarbonyl (Troc), 9-fluorenyl methoxycarbonyl (Fmoc), 2,2,2-trichloroethoxymethyl, trimethyl silyl, triethyl silyl, dimethyl(t-butyl) silyl, diethylmethylsilyl, dimethyl phenylsilyl, diphenylmethylsilyl, acetyl, chloroacetyl, dichloroacetyl trichloroacetyl or trifluoroacetyl.