onto cracked ice. The title compound precipitated as a white solid. Filtration, washing with water, and air-drying gave the product: 0.93 g (66.5%); mp 145 °C. Recrystallization from ethyl acetate provided the analytical sample: mp 147-148 °C; NMR (Me2SO-de) 5.98 (s, 2, CH2), 7.95 (s, 1, H-2), 9.75 (hr s, 1, NH); mass spectrum (70 eV), m/e (relative intensity) 188 (M+, 23), 142

Most peptides have not proved useful as neuroactive drugs because they are blocked by the blood-brain barrier and do not reach their receptors within the brain.Intraperitoneally administered L-serinyl JD-glucosde aalgues of [Metslenkephaln (glycopeptides) have been shown to be transported across the blood-brain barrier to bind with targeted p and &oplod receptors in the mouse brain. The opioid nature of the bing has been demonstrated with intracerebroventricularly a ered naloxone. Paradoxically, glucosylation decreases the ipophlt of the peptides while promoting transport across the phc endothe layer. It is suggested that glucose transporter GLUT-1 is responsible for the transport of the peptide message. Profound and long-lasting anesla has been observed in mice (tail-ck and hot-plate assays) with two of the glycopeptide a ues when administered intraperitoneally.

We have previously reported the chemistry and antinociceptive properties of a series of glycosylated enkephalin analogs (glycopeptides) exhibiting approximately equal affinity and efficacy at ␦ opioid receptors (DORs) and opioid receptors (MORs).

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