Hydrogen Bromide → HCID 10757164, compound

Participants

Reaction Conditions

Reaction Steps

With precursor 19 in hand, all that remained in the synthesis of stevensine (2) was the elimination of HBr. The direct removal of HBr involves a syn elimination event, a process that proved troublesome when tried under basic conditions. Therefore, an acid promoted elimination was attempted since the salts of AI heterocycles are generally quite stable. Heating 19 in methanesulfonic acid (90° C., sealed flask, 12 h) afforded products 3-debromostevensine (20) and 5-bromo-3-debromostevensine (21) in 14% and 47% yields, respectively (Scheme 3).19 The molecular skeleton of 20 and 21 was established by hydrogenation to 2,3-debromohymenin (15). The bromo substitution pattern in 20 and 21 was deduced from their 1H NMR spectra. The a-bromo substituted pyrrole showed b-pyrrole hydrogens at 6.42 (s) ppm and 6.10 (s) ppm for 20 and 21 in CD3OD, respectively.

Provenance & Evidence