New process for the production of oxabispidines

Abstract

There is provided a process for the preparation of a compound of formula I, or a pharmaceutically acceptable derivative thereof, wherein A, B, G, R 1 , R 2 , R 3 , R 4 and R 41 to R 46 have meanings given in the description, which process comprises the dehydrative cyclisation of a compound of formula II,

1 - 40 . (canceled) 
   
   
       41 . A compound of formula VII 
     
       
         
         
             
             
         
       
     
     wherein
 R 1a  represents straight- or branched-chain C 1-4  alkyl terminated by C(O)R 5a  or 
 —N(H)C(O)OR 10b ; 
 R 5a  and R 10b  independently represent straight- or branched-chain C 2-6  alkyl. 
 
   
   
       42 . The compound [2-(9-oxa-3,7-diazabicyclo[3.3.1]non-3-yl)ethyl]carbamic acid tert-butyl ester.