Asymmetric reduction of chlorinated 4-oxopentanoates with Bakers' yeast. Synthesis of optically active .gamma.-butyrolactones and useful chiral building blocks
Palladium-catalyzed asymmetric synthesis of allylic alcohols from unsymmetrical and symmetrical racemic allylic carbonates featuring C–O-bond formation and dynamic kinetic resolution
作者:Hans-Joachim Gais、Oleg Bondarev、Ralf Hetzer
DOI:10.1016/j.tetlet.2005.07.044
日期:2005.9
Described is the asymmetricsynthesis of the allylicalcohols 11 (85% ee), 15 (99% ee), 17 (93% ee), 19 (61% ee), and 21 (69% ee) through a Pd-catalyzed reaction of the unsymmetrical carbonates rac-10, rac-12, rac-14, rac-16, rac-18, and rac-20, respectively, with KHCO3 and H2O in the presence of bisphosphane 6. Similarly the allylicalcohols 23 (99% ee) and 25 (97% ee) have been obtained from the symmetrical
tetrasubstituted carboncenter; and 3) an intramolecularchirality‐transferring Michael reaction of the ketoester, with neighboring‐group participation, to introduce a chiralcenter at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)‐(15S,16R)‐16‐hydroxy‐16,22‐dihydroapparicine and its intermediate against chloroquine‐resistant Plasmodium falciparum (K1 strain)
Palladium-Catalyzed Asymmetric <i>O</i>-1,5-Addition with Oximes via Hydroximation of Unsaturated Esters
作者:Ai-Jun Han、Qitao Tan、Zhi-Tao He
DOI:10.1021/acs.orglett.3c03687
日期:2024.1.12
we disclose an electronically mismatched 1,5-conjugate addition process with oximes as the nucleophiles. By this design, the oxime moieties are readily introduced to the γ-position of the electron-deficient substrates in good yields, excellent regioselectivities, and high enantioselectivities. The corresponding allyl oximes are also conveniently transformed into a series of valuable enantioenriched
Conformational study of chiral alkenes: the influence of protective groups on the relative stability of ground-state rotational isomers
作者:Benjamin W. Gung、Mark A. Wolf
DOI:10.1021/jo00077a023
日期:1993.12
A variable temperature NMR study shows that a protective group on the hydroxy function of a chiral allylic alcohol can either enhance or counter the influence of the vinyl substituent on the ground-state (GS) conformations. If the allylic hydroxy is protected as a methyl ether, the CH-eclipsed form I becomes favored to a greater degree for normal chiral alkenes. Furthermore, conformer I becomes preferred even for the gamma-hydroxy-alpha,beta-unsaturated esters, which normally favor the CO-eclipsed form (II). On the other hand, the tert-butyldimethylsilyl (TBDMS) ether enhances the preference for conformer II for the gamma-hydroxy-alpha,beta-unsaturated esters and diminishes the preference for the CH-eclipsed form of normal chiral alkenes. These facts are explained by the size of the allylic oxygen lone pairs.