The Synthesis of [4-Carboranylalanine, 5-Leucine]-Enkephalin (Including an Improved Preparation of t-Butoxycarbonyl-L-o-carboranylalnine, New Derivatives of L-Propargylglycine, and a Note on Melanotropic and Opiate Receptor Binding Characteristics)
✍ Scribed by Jean-Luc Fauchère; Othmar Leukart; Alex Eberle; Robert Schwyzer
- Publisher
- John Wiley and Sons
- Year
- 1979
- Tongue
- German
- Weight
- 646 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The title compound, an analogue of [Leu^5^]‐enkephalin with L‐o‐carboranylalanine replacing L‐phenylalanine in position 4, was prepared by fragment condensation. The analogue has a 3‐fold higher affinity for rat brain opiate receptors in the [^3^H]naloxone competition assay than natural [Leu^5^]‐enkephalin. Like [Leu^5^]‐enkephalin and N^a^‐acetyl‐[Leu^5^]‐enkephalin, the N‐terminal tripeptide fragment, H · Tyr‐Gly‐Gly · OH, had no melanotropic activity in the Rana pipiens frog skin assay.
A convenient, direct synthesis of methyl t‐butoxycarbonyl‐L‐propargylglycinate is described, and the ^13^C‐NMR. spectra of L‐o‐carboranylalanine recorded. The procedure was extended to the preparation of BOC · Car‐Leu · OMe from BOC · Pra‐Leu · OMe. A number of new propargylglycine derivatives are reported.