Trifluoroacetic acid → (5S,8S,11S,12R)-11-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-5,8-diisopropyl-12-methoxy-4,10-dimethyl-3,6,9-trioxo-2-oxa-4,7,10-triazatetradecan-14-oic acid

Participants

Reaction Steps

To #7 (32 g, 46 mmol, 1 eq.) in dichloromethane (160 mL, 0.29 M) was added drop-wise over 10 minutes trifluoroacetic acid (17.4 mL, 231 mmol, 5 eq.). After 6 hours, the same amount of trifluoroacetic acid was added and the reaction was continued for 18 hours. The reaction mixture was diluted with toluene (320 mL) and concentrated in vacuo to provide #8 (35.8 g, 97%) as a pinkish oil, which was used in the next step without further purification. 1H NMR (400 MHz, DMSO-d6), presumed to be a mixture of rotamers, characteristic signals: δ 7.90 (d, J=7.0 Hz, 2H), 7.62 (d, J=7.4 Hz, 2H), 7.41 (br dd, J=7.4, 7.0 Hz, 2H), 7.29-7.35 (m, 2H), 4.54-4.68 (br m, 1H), [4.09 (d, J=11 Hz) and 4.22 (d, J=10.9 Hz), total 1H], 3.74-3.84 (br m, 1H), 3.22 and 3.24 (2 br s, total 3H), 2.94 and 2.96 (2 br s, total 3H), 2.78 and 2.80 (2 br s, total 3H), 2.13-2.24 (m, 1H), 1.89-2.10 (br m, 2H), 1.70-1.81 (br m, 1H).

Provenance & Evidence