Journal article

Publication year: 2005

Pages: 2012-2018

Journal: Chemistry - A European Journal

Volume number: 11

Issue number: 7

ISSN: 0947-6539

DOI Link: https://doi.org/10.1002/chem.200401027

Publisher: Wiley

Abstract: 
Epoxidation of bullvalene (1) with a neutralized solution of Oxone gave racemic trisepoxide rac-6 in 93% isolated yield. Its structure was examined by X-ray crystallography. The two enantiomers of 6 were separated by preparative HPLC and exhibited specific rotations of [alpha](D)(25) = + 160, [alpha](365)(25) + 567 (c=0.946, CHCl3) for the firstly eluted and [alpha](D)(25) = -157, [alpha](365)(25) = -554 (c = 0.986, CHCl3) for the secondly elated enantiomer of 6. The geometry of (+)-6 and the absolute configuration of (-)-6 were determined by X-ray crystal structure analysis and anomalous diffraction, respectively. According to this, (-)-6 possesses (3R,5S,7S,9R,11R,13S)- and (+)-6 has (3S,5R,7R,9S,11S,13R)-configuration. Upon treatment with BF3 (.) Et2O at -78 degrees C, trisepoxide rac-6 rearranges with retention of the skeletal three-membered carbocycle to give the cage trisether rac-8, as proved by X-ray crystal structure analysis, in virtually quantitative yield. Enantiomers of rac-8 were separated by preparative HPLC and exhibited specific rotations of [alpha](D)(25) = +49, [alpha](365)(25) = +170 (c - 1.01, D 365 CHCl3) (firstly eluting) and [alpha](D)(25) = -46, D [alpha](365)(25) = -160 (c-1.02, CHCl3) (secondly eluting enantiomer). The absolute configuration of (-)-8 was deter-mined by anomalous diffraction to be (1R,3R,7R,9R,11R,13R). DFT computations at the TD-B3LYP/631 + G(d,p)//B3LYP/6-31 + G(d) level of theory for (3R,5S,7S,9R,11R,13S)-6 and (1R,3R,7R,9R,11R,13R)-8 predicted specific rotations of -206.7 and -83.4, respectively. Acid-catalyzed isomerization of the enantiomerically pure (+)-6 proceeded without racemization to give exclusively (-)-8, and (-)-6 provided only (+)-8. Thus, this isomerization occurs with ring opening of the three C-O bonds in the epoxide moieties in the a-position relative to the three-membered carbocycle rather than in the beta-position.

Harvard Citation style: Liang, S., Lee, C., Kozhushkov, S., Yufit, D., Howard, J., Meindl, K., et al. (2005) Bullvalene trisepoxide and its stereospecific rearrangement to 2,8,12-trioxahexacyclo[8.3.0.0(3,9)0(4,6)0(5,13)0(7,11)]tridecane: Two new C-3-symmetrical oligocycles with propeller chirality, Chemistry - A European Journal, 11(7), pp. 2012-2018. https://doi.org/10.1002/chem.200401027

APA Citation style: Liang, S., Lee, C., Kozhushkov, S., Yufit, D., Howard, J., Meindl, K., Ruhl, S., Yamamoto, C., Okamoto, Y., Schreiner, P., Rinderspacher, B., & de Meijere, A. (2005). Bullvalene trisepoxide and its stereospecific rearrangement to 2,8,12-trioxahexacyclo[8.3.0.0(3,9)0(4,6)0(5,13)0(7,11)]tridecane: Two new C-3-symmetrical oligocycles with propeller chirality. Chemistry - A European Journal. 11(7), 2012-2018. https://doi.org/10.1002/chem.200401027