RESUMO
The energetic viability of several mechanistic variations of the reductive amination of acetophenones via the Borch approach was re-examined through density functional theory calculations. The crucial involvement of the acid catalyst is evident not only in the elimination of water, but also in the initial nucleophilic step. This role increases with the electron-donating capability of the substituent positioned at the para-position of acetophenone.
RESUMO
The males-produced pheromone blend of the Mormidea v-luteum (Hemiptera, Pentatomidae) consists in two isomers of zingiberenol (1) and three of murgantiol (2). While the absolute configuration of the zingiberenol isomers has been described, the configurations of the murgantiol isomers remained unexplored. So, our objective was to identify the absolute configuration of the murgantiol isomers (2 a-c) in the pheromone blend. To achieve this, we initially performed dehydration of the natural extract followed by enantiomeric resolution and, as a result, the three isomers was identified as (4R,1'S)-murgantiol. By leveraging the fixed cis and trans relationships among all pheromone components, we established the configuration at C-1 for isomers 2 a and 2 b is S, while that of 2 c is R. Finally, employing microchemical Sharples asymmetric dihydroxylation and epoxide ring closure, we determined the absolute configuration of the epoxide ring. Consequently, the natural isomers 2 a, 2 b, and 2 c were identified as (1S,4R,1'S,4'R)-, (1S,4R,1'S,4'S)-, and (1R,4R,1'S,4'S)-murgantiol, respectively.