Botrydial synthetic studies. Asymmetric synthesis of quaternary carbon centres.
作者:Franz Kunisch、Kurt Hobert、Peter Welzel
DOI:10.1016/s0040-4039(00)98227-3
日期:1985.1
The synthesis of opticallyactive 4 has been accomplished by asymmetricformation of cyclic β-keto esters fully substituted at the α-carbon followed by chemoselective reduction of the ester group. Of the asymmetric reactions examined the Koga procedure proved to be the most selective.
Exploiting steric shielding: Tuning terpenoid-derived oxazolidin-2-ones as chiral auxiliaries for the Diels-Alder reaction
作者:Malcolm R. Banks、Alexander J. Blake、Angus R. Brown、J.I.G. Cadogan、Suneel Gaur、Ian Gosney、Philip K.G. Hodgson、Paul Thorburn
DOI:10.1016/0040-4039(94)85088-7
日期:1994.1
Preparative methodology is described for access to three different terpenoid-derivedoxazolidin-2-ones 4, 8, and 11, of which the latter, obtained from camphene in four steps, provides virtually complete asymmetric induction when acting as a chiralauxiliary in Diels-Alder cycloaddition reactions with cyclopentadiene.
Reactions of<i>t</i>-Butylphosphine–Borane with Various Electrophiles and Synthesis of Optically Active<i>t</i>-Butylmethylphosphine–Borane
作者:Nobuhiko Oohara、Tsuneo Imamoto
DOI:10.1246/bcsj.75.1359
日期:2002.6
The reactivity of t-butylphosphine–borane toward various electrophiles was studied with a focus on alkylation. Monoalkylation of this compound proceeded smoothly in good yields (61–85%). Disubstituted derivatives were also synthesized in good yields (86–99%). Optically active t-butylmethylphosphine–borane was prepared from t-butylphosphine–borane by resolution of intermediate diastereomers of (1S)-endo-2-bornyloxycarbonyl(t-butyl)methylphosphine-borane.
The preparation of the (6R)- and (6S)-diastereoisomers of 5-formyltetrahydrofolate (leucovorin)
作者:Jonathan Owens、Lilias Rees、Colin J. Suckling、Hamish C. S. Wood
DOI:10.1039/p19930000871
日期:——
The separation of the (6R)- and (6S)-diastereoisomers of tetrahydrofolic acid by derivatisation on N-5 with chiral auxiliary reagents followed by fractional crystallisation or extraction is described. Chloroformates of chiral alcohols were used as chiral auxiliaries and those derived from cyclic terpene alcohols were found to be most effective for the separation. The cleavage of the derivative and conversion
A Simple Strategy for the Preparation of <i>P</i>
-Chirogenic Trost Ligands with Different Absolute Configurations
作者:Peng Du、Xiao-Bing Lu
DOI:10.1002/ejoc.202000833
日期:2020.8.23
A simple, short and convenient route towards P‐chirogenic Trost ligands obviates the use of chiral auxiliaries and enables the access to diphosphines with differently configured P‐stereocenters.