Rate of lactamization of benzylstrychnine in acid solution

Abstract

The rate of lactamization of benzylstrychnine in aqueous solution at 25 °C increases with acid concentration up to 5–10% sulfuric acid, and thereafter decreases. The maximum can be explained by taking account of the extent of protonation of the aromatic amino group with increasing acid concentration. This amino group is unusually weakly basic [Formula: see text], perhaps because it is locked in an extremely rigid cage structure which opposes the rehybridization of N which must take place when it is protonated.

Basicity (pK BH+ ) and acidity constants (pK a*) of some 3-X-, 4-X-, and 2,6-dimethyl-4-X-benzoic acids

“…0.33 units too negative. 20 Experimental pKBH+ values for BAc and DMBAc have been correlated with c and C + substituent con~tants,~' and the results are reported in eqns. (4)<7) in the form ( -ApKBH+) us.…”

Structural and chiroptical analysis of naturally occurring (–)-strychnine

“…However, this reaction is important for the isostrychnine-strychnine conversion [18]. Likewise, a lactamization reaction is much too slow to produce ring-opened derivatives during the measurements [23], but could be relevant for the isostrychnine-strychnine conversion.…”