Versatile Asymmetric Synthesis of the Kavalactones: First Synthesis of (+)-Kavain
作者:Thomas E. Smith、Mabel Djang、Alan J. Velander、C. Wade Downey、Kathleen A. Carroll、Sophie van Alphen
DOI:10.1021/ol0493960
日期:2004.7.1
Three asymmetric pathways to the kavalactones have been developed. The first method is chiral auxiliary-based and utilizes aldol reactions of N-acetyl thiazolidinethiones followed by a malonate displacement/decarboxylation reaction. The second approach uses the asymmetric catalytic Mukaiyama additions of dienolate nucleophile equivalents developed by Carreira and Sato. Finally, tin-substituted intermediates, prepared by either of these routes, can serve as advanced general precursors of kavalactone derivatives via Pd(0)-catalyzed Stille couplings with aryl halides.
New C-4-chiral 1,3-thiazolidine-2-thiones: excellent chiral auxiliaries for highly diastereo-controlled aldol-type reactions of acetic acid and .alpha.,.beta.-unsaturated aldehydes
Stereoselective aldol additions of titanium enolates of N-acetyl-4-isopropyl-thiazolidinethione
作者:Mathis B. Hodge、Horacio F. Olivo
DOI:10.1016/j.tet.2004.08.008
日期:2004.10
The addition of chlorotitanium enolates of N-acetyl isopropyl thiazolidine-2-thione to aldehydes was investigated. The stereoselectivity of the aldol products was controlled by the number of equivalents of base added. The syn aldol product was obtained preferentially when 2 equiv of Lewis acid and 1 equiv of base were employed. The anti aldol product was obtained preferentially when 1 equiv of Lewis acid and 2 equiv of base were employed for unsaturated aldehydes. Unexpected results were found with hindered aldehydes when 2 equiv of base were employed. (C) 2004 Elsevier Ltd. All rights reserved.
The synthesis of a C1-C8 lactone fragment of discodermolide
作者:Julian M.C. Golec、Stuart D. Jones
DOI:10.1016/s0040-4039(00)61479-x
日期:1993.12
The assymetric synthesis of a fragment corresponding to the C-1-C-8 region of the immunosuppressant dicodermolide is reported. A trihydroxylactone of defined absolute stereochemistry is also prepared. This compound is a potential reductive ozonolysis product of discodermolide and may aid the determination of the absolute stereochemistry or the natural product
Asymmetric acetate aldol reactions in connection with an enantioselective total synthesis of macrolactin A
Asymmetric aldol-like reactions of cinnamaldehyde, dienal 3 (fragment C7-C12 of macrolactin A), and dienal 4 (fragment C15-C24) with (i) chiral acetylthiazolidinethione-derived enolates, (ii) chiral boron enolates, and (iii) silyl enolates in the presence of chiral titanium-2,2'-dinaphthol complexes are compared. Use of the thiazolidinethione auxiliary and TiCl4 shows practical advantages; e.g., C5-C12 fragment 7 has been isolated enantiomerically pure in 74% yield. Copyright (C) 1996 Elsevier Science Ltd