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

9.1 g of the crude product N-[(9H-fluoren-9-ylmethoxy)carbonyl]-N-methyl-L-valyl-N-[(3R,4S,5S)-1-tert-butoxy-3-methoxy-5-methyl-1-oxoheptan-4-yl]-N-methyl-L-valinamide (Intermediate 3) were taken up in 56.6 ml of dichloromethane, 56.6 ml of trifluoroacetic acid were added, and the mixture was stirred at RT for 2 h. Subsequently, the reaction mixture was concentrated under reduced pressure and the remaining residue was purified by flash chromatography, using dichloromethane, 3:1 dichloromethane/ethyl acetate and 15:5:0.5 dichloromethane/ethyl acetate/methanol as eluent. After purification of the corresponding fractions and concentration, 5.8 g (86% of theory) of the title compound were obtained as a colourless foam.

Provenance & Evidence