Enantioselective allene/enone photocycloadditions: The use of an inexpensive optically active 1,3-disubstituted allene
作者:Mary S. Shepard、Erick M. Carreira
DOI:10.1016/s0040-4020(97)01013-2
日期:1997.12
and use of an inexpensive readily prepared opticallyactive 1,3-disubstituted allene that may be utilized for enantioselective intramolecular allene/enone photocycloadditions. In addition, we describe novel substrates for intramolecular [2+2] photocycloadditions which substantially expand the scope of the process to include amino- and thio- tethered allene/enones.
The invention is drawn to compounds of the formula ##STR1## wherein R.sup.1 and R.sup.2 are hydrogen or acyl; provided that only one of R.sup.1 or R.sup.2 is hydrogen, useful in the treatment of hyperproliferative skin diseases and sebaceous gland diseases.
Diarylprolinol in an Asymmetric, Direct Cross-Aldol Reaction with Alkynyl Aldehydes
作者:Yujiro Hayashi、Masahiro Kojima、Yusuke Yasui、Yuta Kanda、Takasuke Mukaiyama、Hiroki Shomura、Daichi Nakamura、Ritmaleni、Itaru Sato
DOI:10.1002/cctc.201300390
日期:2013.10
The direct cross‐aldol reaction of alkynyl aldehydes catalyzed by a trifluoromethylated diarylprolinol provides a practical route for the highly enantioselective synthesis of chiral β‐alkynyl‐β‐hydroxy aldehydes. Good anti selectivity and excellent enantioselectivity were obtained in the reactions of silylpropynals, which afford synthetically useful chiral building blocks.
Total synthesis of 25-Hydroxy-16,23E-diene Vitamin D3 and 1α,25-Dihydroxy-16,23E-diene Vitamin D3: separation of genomic and nongenomic vitamin D Activities
作者:Marek M. Kabat、Walter Burger、Sandra Guggino、Bernard Hennessy、Jerome A. Iacobelli、Kazuhiro Takeuchi、Milan R. Uskokovic
DOI:10.1016/s0968-0896(98)00164-3
日期:1998.11
Separation of genomic and nongenomic vitaminD activities was achieved by structural modification of 1,25-dihydroxy vitaminD3 by introduction of 16 and 23E double bonds. The modified compound 3, lacking a 1 alpha-hydroxy group, exhibits only nongenomic activity. Its 1 alpha-hydroxy relative 4 expresses fully both genomic and non-genomic activities. A total synthesis of analogues 3 and 4 is described
Catalytic, enantioselective acetate aldol additions to α,β-ynals: Preparation of optically active propargylic alcohols
作者:Robert A. Singer、Mary S. Shepard、Erick M. Carreira
DOI:10.1016/s0040-4020(98)00344-5
日期:1998.6
A catalytic, enantioselective acetate-aldol addition reaction of silyl ketene acetals with α,β-ynals and 3 mol % of a chiral Ti(IV) complex is described. This process provides access to opticallyactive β-hydroxy-γ-alkynyl esters in 84–96% yields and 94–97% ee's.