L-Tyrosine, N-(1,1-dimethylethoxy)carbonyl- → HCID 15296358, compound

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Reaction Steps

Compound (U) (3.51 g, 10 mmol) was dissolved in a solution of 25% TFA in DCM (10 ml) and stirred at room temperature for 30 mins. The solution was evaporated to dryness in vacuo and the residue evaporated from DCM three more times to remove residual traces of TFA. This residue was coupled to Boc-tyrosine (2.8 g, 10 mmol) using the procedure described for the synthesis of compound (U). The resultant product was purified by column chromatography (silica; 50% ethyl acetate in hexane (Rf =0.19)) as a colourless powder (4.9 g, 96%), mp 96-100° C. 1H NMR (CDCl3): δ 6.7-7.1 (m, 6H, ArH, Ile-NH, NH), 5.15 (d, J=8.2 Hz, 1H, Tyr-NH), 4.30 (m, 1H, αCH), 4.2 (m, 1H, αCH), 3.35-3.50 (m, 1H, NCH), 3.40 (t, J=6.0 Hz, 2H, CH2Br), 3.25 (m, 1H, NCH), 3.01 (dd, J=6.1, 13.6 Hz, 1H, Tyr-βCH), 2.93 (dd, J=6.1, 13.6 Hz, 1H, Tyr-βCH), 2.05 (m, 2H, CH2), 1.9 (m, 1H, Ile-βCH), 1.4 (m, 10H, Ile-γCH, (CH3)3), 1.05 (m, 1H, Ile-γCH), 0.89 (d, J=6.32 Hz, 3H, Ile-γCH3), 0.83 (t, J=7.37 Hz, 3H, Ile-δCH3). ISMS 514/516 (M+H). HRMS calcd for C23H35N3O5 (M-HBr), 433.2577; found 433.2573.

Provenance & Evidence