410523-53-4Relevant articles and documents
Asymmetric total synthesis of (-)-callystatin A and (-)-20-epi-callystatin A employing chemical and biological methods
Enders, Dieter,Vicario, Jose L.,Job, Andreas,Wolberg, Michael,Mueller, Michael
, p. 4272 - 4284 (2007/10/03)
An efficient asymmetric total synthesis of the potent cytotoxic marine natural product (-)-callystatin A and its 20-epi analogue has been achieved. The synthetic pathway involved the preparation of three fragments to be coupled with each other at the end of the route. The first fragment 3 was obtained using a biocatalytic enantioselective reduction of a 3,5-dioxocarboxylate as the key step. For the second intermediate 4 the asymmetric α-alkylation of an O-protected derivative of 4-hydroxybutanal was performed exploiting the SAMP/ RAMP hydrazone alkylation methodology, and followed by a highly Z-selective Homer-Wadsworth-Emmons reaction under modified conditions. For the synthesis of the polypropionate fragment 5 a diastereoselective syn-aldol reaction was employed between a chiral ethyl ketone and an α-substituted chiral aldehyde, both prepared in enantiopure form again by means of the asymmetric alkylation of their corresponding RAMP hydrazones. Finally, these three building blocks were coupled using highly E-selective Wittig reactions via allyltributylphosphonium ylides to afford the target compounds after a final oxidation/deprotection sequence.
Oxabicyclo[3.2.1]oct-6-enes as templates for the stereoselective synthesis of polypropionates: Total synthesis of callystatin a and C19-epi-callystatin A
Lautens, Mark,Stammers, Timothy A.
, p. 1993 - 2012 (2007/10/03)
The total synthesis of the polyketide natural product callystatin A and its novel analog C19-epi-callystatin A is described. Our strategy features the use of an enantiomerically pure oxabicyclo[3.2.1]oct-6-ene as a template for the stereocontrolled preparation of the C15-C21 polypropionate region.
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 (2007/10/03)
(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.