TY - JOUR
T1 - Studies in sigmatropic rearrangements of N-prenylindole derivatives - A formal enantiomerically pure synthesis of tryprostatin B
AU - Cardoso, A. Sofia P.
AU - Marques, M. Manuel B.
AU - Srinivasan, Natarajan
AU - Prabhakar, Sundaresan
AU - Lobo, Ana M.
AU - Rzepa, Henry S.
PY - 2006/10/25
Y1 - 2006/10/25
N2 - Rearrangement of Na-prenyl-Nb-acetyltryptamine, induced by BF3·Et2O at low temperature, leads to a 2-prenyl derivative, and thence to the tricyclic tryptamine 7 and the indoline 8. Similarly, Na-prenyl-Nb-phthaloyl-l-tryptophan methyl ester furnished the corresponding 2-prenyl derivative 16, a known advanced precursor of tryprostatin B. Density functional (B3LYP) calculations for the putative rearrangement transition state for N-prenylskatole show that prior coordination of BF3 to the indolic nitrogen changes the character of the subsequent sigmatropic pericyclic shifts from being entirely covalent to acquiring a significant degree of ionic character. The shifting prenyl group favours the endo over the exo mode of the transition state by 4.1 kcal mol -1.
AB - Rearrangement of Na-prenyl-Nb-acetyltryptamine, induced by BF3·Et2O at low temperature, leads to a 2-prenyl derivative, and thence to the tricyclic tryptamine 7 and the indoline 8. Similarly, Na-prenyl-Nb-phthaloyl-l-tryptophan methyl ester furnished the corresponding 2-prenyl derivative 16, a known advanced precursor of tryprostatin B. Density functional (B3LYP) calculations for the putative rearrangement transition state for N-prenylskatole show that prior coordination of BF3 to the indolic nitrogen changes the character of the subsequent sigmatropic pericyclic shifts from being entirely covalent to acquiring a significant degree of ionic character. The shifting prenyl group favours the endo over the exo mode of the transition state by 4.1 kcal mol -1.
UR - http://www.scopus.com/inward/record.url?scp=33750148087&partnerID=8YFLogxK
U2 - 10.1039/b606457d
DO - 10.1039/b606457d
M3 - Article
C2 - 17047877
AN - SCOPUS:33750148087
SN - 1477-0520
VL - 4
SP - 3966
EP - 3972
JO - Organic & Biomolecular Chemistry
JF - Organic & Biomolecular Chemistry
IS - 21
ER -