Amino acids and peptides. LI. Application of the 2- adamantyloxycarbonyl (2-Adoc) group to the protection of the hydroxyl function of tyrosine in peptide synthesis

Article abstract of DOI:10.1248/cpb.45.1860

A 2-adamantyloxycarbonyl (2-Adoc) group was introduced as a protecting group for the hydroxyl function of tyrosine (Tyr) through the Shotten- Bauman reaction of 2-adamantyloxycarbonyl chloride with the copper complex of Tyr. The 2-Adoc group is stable to trifluoroacetic acid (TFA), 5.0 N HCl/dioxane, hydrogenation over a Pd catalyst and tertiary amine, and is easily removed by treatment with 1M trifluoromethanesulfonic acid (TFMSA)- thioanisole/TFA and HF. Boc-Tyr(2-Adoc)-OH was prepared by the reaction of (Boc)₂O and H-Tyr(2-Adoc)-OH in the presence of triethylamine. Boc-Tyr(2- Adoc)-OH was successfully applied to the synthesis of Boc-Ala-Thr-Val- Lys(2-Adoc)-Phe-Lys(2-Adoc)-Tyr(2-Adoc)-Gly-OH, corresponding to the sequence 1-9 of Sulfolobus solfataricus RNase, and Boc-Tyr(2-Adoc)-Asp(O- 2-Ada)-Glu(O-cHex)-Gly-OH, corresponding to the sequence 33-36 of S. solfataricus RNase. Boc-Phe-Lys(2-Adoc)-Tyr(2-Adoc)-Lys(2-Adoc)-Gly-OBzl was treated with anhydrous HF to afford H-Phe-Lys-Tyr-Gly-OH without any side reactions, in a good yield.

Full text of DOI:10.1248/cpb.45.1860

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