(D)-2-tert-Butoxycarbonylamino-5,5-difluoro-5-phenyl-pentanoic acid: synthesis and incorporation into the growth hormone secretagogues.

The first enantioselective synthesis of (d)-2-tert-butoxycarbonylamino-5,5-difluoro-5-phenyl-pentanoic acid 3 was achieved. The incorporation of the titled compound into growth hormone secretagogue (GHS) compounds resulted in new analogs 10 and 16, both of which had significantly increased in vitro potency. The compound 10 also showed improved in vivo efficacy as well as pharmacokinetic properties in rat models.