Purification of precursor compound by crystallisation

摘要

The invention relates to a process for preparation of radiopharmaceutical precursors, and in particular protected amino acid derivatives which are used as precursors for production of radiolabelled amino acids for use in vivo imaging procedures such as positron emission tomography (PET). Particularly, the invention relates to a process for preparation of a precursor useful in the preparation of the [18F]-1-amino-3-fluorocyclobutanecarboxylic acid ([18F] FACBC) PET tracer.

主权项

1. A method to obtain a compound of Formula I: wherein: R1 represents a C1-5 straight- or branched-chain alkyl group; R2 represents an amino protecting group; v is an integer of 0 to 4; and, X represents a leaving group selected from a halogen, or the group —O—SO2—R3 wherein R3 is a halogen, a straight-chain or branched-chain C1-10 alkyl, a straight-chain or branched-chain C1-10 haloalkyl, and a C6-10 aryl wherein said method comprises: (a) debenzylation of a compound of Formula Ia: wherein R11, R12 and w are as defined for R1, R2 and v of Formula I, respectively; (b) crystallisation of the reaction mixture from step (a) to obtain purified compound of Formula Ib: wherein R21, R22 and x are as defined for R1, R2 and v of Formula I, respectively (c) conversion of purified compound of Formula I obtained in step (b) into a compound of Formula I by reaction with a suitable form of X wherein X is as defined for Formula I.