404958-08-3Relevant articles and documents
Asymmetric total synthesis of (-)-callystatin A employing the SAMP/RAMP hydrazone alkylation methodology
Vicario, Jose L.,Job, Andreas,Wolberg, Michael,Mueller, Michael,Enders, Dieter
, p. 1023 - 1026 (2002)
(equation presented) The asymmetric total synthesis of (-)-callystatin A has been achieved. The key steps generating the stereogenic centers rely on the asymmetric α-alkylation of aldehydes or ketones exploiting the SAMP/RAMP hydrazone alkylation methodology, as well as an enzymatic enantioselective reduction of a 3,5-dioxocarboxylate. For the construction of the alkene moieties, highly selective Wittig or Horner-Wadsworth-Emmons reactions were employed.
Regio and enantioselective reduction of t-butyl 6-chloro-3,5-dioxohexanoate with baker's yeast
Wolberg, Michael,Kaluzna, Iwona A.,Mueller, Michael,Stewart, Jon D.
, p. 2825 - 2828 (2007/10/03)
Whole baker's yeast cells reduce t-butyl 6-chloro-3,5-dioxohexanoate regioselectively to the corresponding C5 hydroxy keto ester. While the (R)-alcohol was favored, the enantioselectivity was poor (41% ee). A variety of process conditions were evaluated in order to improve both the enantioselectivity and yield of this reduction. Including a nonpolar resin in the reaction mixture afforded the (R)-alcohol in 94% ee and 50% isolated yield. The enantioselectivity was further improved to >99% ee by substituting purified YGL157w in place of whole yeast cells. This reductase was identified by screening a collection of yeast enzymes uncovered by genome sequence analysis.
