| abstract |
There is provided a process for the preparation of a compound of formula (7) or salts thereof: wherein R1 represents a hydrogen or a hydrocarbyl group, R2 represents a hydrogen or substituent group, R3 represents a hydrogen or a hydrocarbyl group, and X represents a hydrogen or substituent group which comprises a) cyanating a compound of formula (1): wherein Y represents a halo group, preferably CI or Br; P1 represents hydrogen or a protecting group, and W represents =0 or -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2): b) reducing the compound of formula (2) to give a compound of formula (3): coupling the compound of formula (3) with a compound of formula (4): to give a compound of formula (5): when W represents -OP2, deprotecting and then oxidising the compound of formula (5) to give a compound of formula (6): and e) subjecting the compound of formula (5) when W represents =O, or compound of formula (6) to ring-opening, and removal of any remaining protecting groups, to give a compound of formula (7) or salts thereof. |