Dipeptide derivatives.

This invention is directed to compounds of the formula (i)and the pharmaceutically-acceptable salts thereof, where the substituents are as defined in the specification, which are growth hormone secretogogues and which increase the level of endogenous growth hormone. The compounds of this invention are useful for the treatment and prevention of owsteoporosis and/or fraily, congestive heart failure, frailty associated with aging, obesity; accelerating bone fracture repair, attenuating protein catabolic response after a major operation, reducing cachexia and protein loss due to chronic illness, accelerating wound healing, or accelerating the recovery of burn patients or patients having undergone major surgery; improving muscle strength, mobility, maintenance os skin thickness, metabolic homeostasis or renal homeostasis. The compounds of the present invention are also useful in treating osteoporosis and/or frailty when used in combination with: a bisphosphonate compound such as alendronate; estrogen, premarin, and optionally progesterone; an estrogen agonist or antagonist; or calcitonin, and pharmaceutical compositions useful therefor. Further, the present invention is directed to pharmaceutical compositions useful for increasing the endogenous production or release of growth hormone in a human or other animal which comprises an effective amount of a compound of the present invention and a growth hormone secretagogue selected from ghrp-6, hexarelin, ghrp-1, growth hormone releasing factor (grf), igf-1, igf-2 or b-ht920. The invention is also directed to intermediates useful in the preparation of compounds of formula i.