1033003-82-5Relevant academic research and scientific papers
The stereocontrolled total synthesis of spirastrellolide A methyl ester. Fragment coupling studies and completion of the synthesis
Paterson, Ian,Anderson, Edward A.,Dalby, Stephen M.,Lim, Jong Ho,Maltas, Philip
, p. 5873 - 5886 (2012/08/28)
The spirastrellolides are a novel family of structurally unprecedented marine macrolides which show promising anticancer properties due to their potent inhibition of protein phosphatase 2A. In the preceding paper, a modular strategy for the synthesis of spirastellolide A methyl ester which allowed for the initial stereochemical uncertainties was outlined, together with the synthesis of a series of suitably functionalised fragments. In this paper, the realisation of this synthesis is described. Two alternative coupling strategies were explored for elaborating the C26-C40 DEF bis-spiroacetal fragment: a modified Julia olefination of a C26 aldehyde with a C17-C25 sulfone, and a Suzuki coupling of a C25 trialkylborane with a C17-C24 vinyl iodide, which also required the development of a double hydroboration reaction to install the C23/C24 stereocentres. The latter proved a significantly superior strategy, and was fully optimised to provide a C17 aldehyde which was coupled with a C1-C16 alkyne fragment to afford the C1-C40 carbon framework. The BC spiroacetal was then installed within this advanced intermediate by oxidative cleavage of two PMB ethers with spontaneous spiroacetalisation, which also led to unanticipated deprotection of the C23 TES ether. The ensuing truncated seco-acid was cyclised in high yield to construct the 38-membered macrolactone under Yamaguchi macrolactonisation conditions, suggesting favourable conformational pre-organisation. Exhaustive desilylation provided a crystalline macrocyclic pentaol, revealing much about the likely conformation of the macrolactone in solution. Attachment of the remainder of the side chain proved challenging, potentially due to steric hindrance by this macrocycle; an olefin cross-metathesis to install an electrophilic allylic carbonate and subsequent π-allyl Stille coupling with a C43-C47 stannane achieved this goal. Global deprotection completed the first total synthesis of (+)-spirastrellolide A methyl ester which, following detailed NMR correlation with an authentic sample, validated the full configurational assignment. A series of simplified analogues of spirastrellolide incorporating the C26-C47 region were also prepared by π-allyl Stille coupling reactions.
The stereocontrolled total synthesis of spirastrellolide A methyl ester. Expedient construction of the key fragments
Paterson, Ian,Anderson, Edward A.,Dalby, Stephen M.,Lim, Jong Ho,Maltas, Philip,Loiseleur, Olivier,Genovino, Julien,Moessner, Christian
, p. 5861 - 5872 (2012/08/28)
Due to a combination of their promising anticancer properties, limited supply from the marine sponge source and their unprecedented molecular architecture, spirastrellolides represent attractive and challenging synthetic targets. A modular strategy for the synthesis of spirastrellolide A methyl ester, which allowed for the initial stereochemical uncertainties in the assigned structure was adopted, based on the envisaged sequential coupling of a series of suitably functionalised fragments; in this first paper, full details of the synthesis of these fragments are described. The pivotal C26-C40 DEF bis-spiroacetal was assembled by a double Sharpless asymmetric dihydroxylation/acetalisation cascade process on a linear diene intermediate, configuring the C31 and C35 acetal centres under suitably mild acidic conditions. A C1-C16 alkyne fragment was constructed by application of an oxy-Michael reaction to introduce the A-ring tetrahydropyran, a Sakurai allylation to install the C9 hydroxyl, and a 1,4-syn boron aldol/directed reduction sequence to establish the C11 and C13 stereocentres. Two different coupling strategies were investigated to elaborate the C26-C40 DEF fragment, involving either a C17-C25 sulfone or a C17-C24 vinyl iodide, each of which was prepared using an Evans glycolate aldol reaction. The remaining C43-C47 vinyl stannane fragment required for introduction of the unsaturated side chain was prepared from (R)-malic acid.
Total synthesis of spirastrellolide A methyl ester - Part 2: Subunit union and completion of the synthesis
Paterson, Ian,Anderson, Edward A.,Dalby, Stephen M.,Lim, Jong Ho,Genovino, Julien,Maltas, Philip,Moessner, Christian
, p. 3021 - 3025 (2008/12/23)
(Figure Presented) Succumbing to synthesis: The stereocontrolled total synthesis of spirastrellolide A methyl ester is reported. The union of two key C1-C16 and C17-C40 subunits is followed by macrolactonization and late-stage side chain attachment by a cross-metathesis reaction anda π-allyl Stille coupling reaction with a C43-C47 stannane, thus confirming the 46R configuration. The full configuration and conformation of the 38-membered macrolide is revealed by single-crystal X-ray analysis of an advanced pentaol intermediate.
