A compound of the formulawhere R1 is H, C1āC4 alkyl and OH; R2 in is H, C1āC4 alkyl and OH; R3 is H and C1āC4 alkyl; R4 is H and C1āC4 alkyl; n is an integer between 0 and 2 inclusive; R5 is a nullity, NHR7C(O)ā, C6H4ā, C6H4āOā; R7 is C2āC6 alkyl; and R6 is a moiety capable of crossing the blood brain barrier and is as a free compound serotonin, dopamine, blood brain barrier (BBB) peptide, membrane translocating peptide, TAT peptides, bradykinin, beta-endorphin, bombesin, calcitonin, cholecystokinin, an enkephalin, dynorphin, insulin, gastrin, substance P, neurotensin, glucagon, secretin, somatostatin, motilin, vasopressin, oxytocin, prolactin, thyrotropin, an angiotensin, galanin, neuropeptide Y, thyrotropin-releasing hormone, gonadotropnin-releasing hormone, growth hormone-releasing hormone, luteinizing hormone, vasoactive intestinal peptidegluconate, transferrin, glucosylamine, amino saccharin, saccharin ester, lactylamine, leucine, tryptophan, amino glutamate and amino cholines.