Atropisomeric properties of 7-, 8-, and 9-membered-ring dibenzolactams: conformation, thermal stability, and chemical reactivity.
The atropisomeric enantiomers of 7-, 8-, and 9-membered-ring dibenzolactams were separated by using chiral HPLC, and their stereochemistries were clarified by using X-ray crystallographic analysis. The atropisomers showed high stereochemical stability with the 8-membered ring being the most stable. In 7- and 8-membered dibenzolactams, highly stereoselective C7-methylation proceeded from the lower side of the ring to provide the products with a C7-methyl group in the pseudoaxial orientation, which converted to thermodynamically more stable isomers with the pseudoequatorial C7-methyl group. In 9-membered dibenzolactam, C7-methylation occurred from the opposite (upper) side of the ring to provide a thermodynamically stable product with the pseudoequatorial C7-methyl group.
Tabata
Hidetsugu
H
School of Pharmaceutical Sciences, Teikyo University, 1091-1, Midori-ku, Sagamihara, Kanagawa 252-5195, Japan.
Suzuki
Hiroyuki
H
Akiba
Kumi
K
Takahashi
Hideyo
H
Natsugari
Hideaki
H
D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D007769:Lactams / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics
D007769:Lactams