Enantioselective total synthesis of altohyrtin C (spongistatin 2)

Evans, David A.; Trotter, B. Wesley; Coleman, Paul J.; Côté, Bernard; Dias, Luiz C.; Rajapakse, Hemaka A.; Tyler, Andrew N.

doi:10.1016/s0040-4020(99)00438-x

Cited by 171 publications

(94 citation statements)

References 115 publications

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“…Concomitant deprotection-cyclisation of ketone 57 with a variety of acids (e.g. aq HF, [37] CSA [37] ) only afforded trace amounts of the target 58 (Scheme 9). On recommendation from a wonderful review by Pihko et al, [38] direct methods for conversion of 52 to 58 (i.e., treatment with HF·py, [39] aq HF [40] or HCl [41,42] ) were then investigated, which unfortunately provided little improvement.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…Considering the effort required to drive cyclisation with acid promoters, and the fact that CAN performed this task extremely well, suggests that formation of the spiroacetal was www.chemeurj.org mediated by metal (namely cerium) templated preorganisation as precedented by Smith [41] and Evans. [37,46] Direct comparison of the optical rotation of both the synthetic material 58 (À16.6) and the natural material 1…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

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Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Dong

Schill

Grange

et al. 2009

Chemistry A European J

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EBC-23, 24, 25, 72, 73, 75 and 76 were isolated from the fruit of Cinnamomum laubatii (family Lauraceae) in the Australian tropical rainforests. EBC-23 (1) was synthesized stereoselectively, in nine linear steps in 8 % overall yield, to confirm the reported relative stereochemistry and determine the absolute stereochemistry. Key to the total synthesis was a series of Tietze-Smith linchpin reactions. The novel spiroacetal structural motif, exemplified by EBC-23 (1), was found to inhibit the growth of the androgen-independent prostate tumor cell line DU145 in the mouse model, indicating potential for the treatment of refractory solid tumors in adults.

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Section: Wwwchemeurjorgmentioning

confidence: 99%

Section: Wwwchemeurjorgmentioning

confidence: 99%

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Dong

Schill

Grange

et al. 2009

Chemistry A European J

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“…O intermediário avançado 21 foi utilizado na síntese do produto natural marinho altoirtina C (espongistatina 2) [30][31][32][33] .…”

Section: Reações Aldólicas Com Estereoindução 15-antiunclassified

Indução assimétrica 1,5-Anti na adição de enolatos de boro de metilcetonas beta-oxigenadas a aldeídos

Dias¹,

Aguilar²

2007

Quím. Nova

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# Esta revisão é dedicada à Prof a . Helena M. C. Ferraz em reconhecimento a sua grande contribuição acadêmica e científica para a área de Química Orgânica no Brasil. High levels of substrate-based 1,5-stereoinduction are obtained in the boron-mediated aldol reactions of β-oxygenated methyl ketones with achiral and chiral aldehydes. Remote induction from the boron enolates gives the 1,5-anti adducts, with the enolate π-facial selectivity critically dependent upon the nature of the β-alkoxy protecting group. This 1,5-anti aldol methodology has been strategically employed in the total synthesis of several natural products. At present, the origin of the high level of 1,5-anti induction obtained with the boron enolates is unclear, although a model based on a hydrogen bonding between the alkoxy oxygen and the formyl hydrogen has been recently proposed. INDUÇÃO ASSIMÉTRICA 1,5-ANTI NA ADIÇÃO DE ENOLATOS DE BORO DE METILCETONASKeywords: 1,5-anti induction; boron enolates; aldol reactions. INTRODUÇÃOA reação aldólica é seguramente um dos métodos mais poderosos para a formação de ligações carbono-carbono 1-7 . Esta reação representa uma ferramenta muito útil na construção de fragmentos com alta complexidade estrutural e com elevados níveis de seletividade, sendo bastante empregada na síntese assimétrica de produtos naturais com atividade farmacológica destacada 8,9 . A incorporação de convergência na construção de policetídeos requer que fragmentos complexos sejam acoplados em algum ponto da rota sintética e, neste sentido, a reação aldólica representa um mé-todo extremamente útil.Os fatores responsáveis pelo controle da estereosseletividade na reação aldólica envolvendo enolatos metálicos estão relacionados com a natureza do átomo do ácido de Lewis utilizado (B, Li, Zn, Ti, Mg etc); a geometria da dupla ligação do enolato preparado (Z ou E); a presença de centros estereogênicos no enolato, no aldeído, ou no ácido de Lewis; o volume e a natureza dos substituintes nos substratos e, as condições reacionais.Em termos gerais, a estereoquímica relativa esperada para os produtos de reações aldólicas envolvendo enolatos de boro E e Z pré-formados é bastante previsível. A reação aldólica com enolatos de boro Z fornece o aduto de aldol syn, e com enolatos de boro E, o aduto de aldol anti, como está delineado no Esquema 1. Estas reações passam por estados de transição cíclico-quelados, do tipo cadeira, como proposto por Zimmerman-Traxler (Esquema 1) 4,10,11 . Neste modelo observa-se que o controle da diastereosseletividade é dependente do volume do substituinte presente no aldeído, que preferencialmente ocupa uma posição pseudo-equatorial no estado de transição tipo cadeira, eliminando dessa maneira a interação 1,3-diaxial desfavorável entre o grupo R e o grupo X.Os parâmetros estéricos influenciam fortemente na formação de estados de transição diastereoisoméricos e, conseqüentemente, na estereoquímica dos produtos obtidos (a geometria do enolato se transfere para o produto em um processo altamente diastereosseletivo). Os dialquil...

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“…After considerable experimentation it was found that the C 2′ -hydroxyl could be selectively methylated using Meerwein's salt and 2,6-di-tert-butyl-4-methylpyridine (DTBMP). 25 The resultant lactone was reduced and acetylated using Rychnovsky's one-pot procedure 26 to yield the six-membered acetate 42 as a 9:1 mixture of anomers. To allow for glycosidation flexibility, the anomeric acetate 42 was converted into both the trichloroacetimidate 43 and the thioglycosides 44 and 45.…”

Section: Synthesis Of Callipeltose 2pmentioning

confidence: 99%

Enantioselective total synthesis of callipeltoside A: two approaches to the macrolactone fragment

Evans

Burch

et al. 2008

Tetrahedron

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The enantioselective total synthesis of callipeltoside A is described. Two syntheses of the macrolactone subunit are included: the first relies upon an Ireland-Claisen rearrangement to generate the trisubstituted olefin geometry and the second utilizes an enantioselective vinylogous aldol reaction for this purpose. Enantioselective syntheses of the sugar and chlorocyclopropane side chain fragments are also disclosed. The relative and absolute stereochemistry of this natural product was determined by fragment coupling with the two enantiomers of the side chain fragment.

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Enantioselective total synthesis of altohyrtin C (spongistatin 2)

Cited by 171 publications

References 115 publications

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Indução assimétrica 1,5-Anti na adição de enolatos de boro de metilcetonas beta-oxigenadas a aldeídos

Enantioselective total synthesis of callipeltoside A: two approaches to the macrolactone fragment

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