Aldol-Type Chirons from Asymmetric Hydrogenations of Trisubstituted Alkenes
摘要:
Catalyst control dominates in the asymmetric hydrogenations of largely unfunctionalized trisubstituted alkenes formed from lactic acid and glyceraldehyde, affording syn- and ant aldol products of the type shown above.
Synthesis of Optically Active β,γ-Unsaturated α-Amino Acids and of α,β-Unsaturated γ-Amino Acids. SN2- vs. SN2’-Dichotomy of the Mitsunobu Amination of Allylic Alcohols
作者:Johann Mulzer、Günther Funk
DOI:10.1055/s-1995-3847
日期:1995.1
Novel and efficient syntheses (6-9 steps, overall yields 10-30%) are described for optically pure β,γ-unsaturated α-amino acids and α,β-unsaturated γ-amino acids, starting from (R)-isopropylidene glyceraldehyde and ethyl (S)-lactate, respectively. The key step is the Mitsunobu reaction of chiral secondary allylic alcohols with phthalimide as the nucleophile, where α,γ allylic transpositions are observed for the first time. The structure-α,γ-ratio-relationship is studied and also the stereochemistry of the allylic transposition. The α-substitution proceeds via clean SN2 inversion, whereas the γ-substitution corresponds to an (E)-anti attack of the nucleophilic with varying stereoselectivities.
work synthetic and semi-synthetic studies toward the antitumor active natural product tonantzitlolone B are described, starting with an advanced intermediate obtained from the total synthesis of tonantzitlolone and a natural sample of this compound, respectively. The unknown absoluteconfiguration of the stereogenic center in the side chain was elucidated to be (R).
Highly Stereoselective Epoxidation of α-Methyl-γ-hydroxy-α,β-unsaturated Esters: Rationalization and Synthetic Applications
作者:Irakusne López、Santiago Rodríguez、Javier Izquierdo、Florenci V. González
DOI:10.1021/jo0709955
日期:2007.8.1
The diastereoselectivity of the nucleophilic epoxidation of gamma-hydroxy-alpha, beta-unsaturated esters having a methyl substituent at the alpha- or beta-position was investigated. Epoxidation of the alpha-methyl-substituted enoate was highly stereoselective, giving rise to the syn isomer. This finding was used to perform an enantioselective synthesis of a natural product having a beta-hydroxy-alpha-methylene-gamma-butyrolactone motif. The nucleophilic epoxidation of enoates was found to be irreversible. Models to explain the observed stereoselectivities are proposed.
Aldol-Type Chirons from Asymmetric Hydrogenations of Trisubstituted Alkenes
作者:Jian Zhao、Kevin Burgess
DOI:10.1021/ol900308w
日期:2009.5.21
Catalyst control dominates in the asymmetric hydrogenations of largely unfunctionalized trisubstituted alkenes formed from lactic acid and glyceraldehyde, affording syn- and ant aldol products of the type shown above.
Koul, Surinder; Crout, David H. G.; Errington, William, Journal of the Chemical Society. Perkin transactions I, 1995, # 23, p. 2969 - 2988
作者:Koul, Surinder、Crout, David H. G.、Errington, William、Tax, Jiri