Magnesium Halide-Catalyzed Anti-Aldol Reactions of Chiral N-Acylthiazolidinethiones

Abstract

[reaction: see text] Diastereoselective direct aldol reactions of chiral N-acylthiazolidinethiones occur in high yield with preference for the illustrated anti diastereomer. This reaction is catalyzed by 10% MgBr2.OEt2 in the presence of triethylamine and chlorotrimethylsilane. Yields range from 56 to 93% with diastereoselectivity up to 19:1 for a variety of N-acylthiazolidinethiones and unsaturated aldehydes.

Synthesis and biological evaluation of truncated α-tubulin-binding pironetin analogues lacking alkyl pendants in the side chain or the dihydropyrone ring

“…35 Biological properties of pironetin analogues Cellular effects of the compounds. We have determined the IC 50 values for pironetin analogues 1-6, as well as for synthetic intermediates (E)-57, (Z)-57 and (Z)-58, and compared these values with that of pironetin on both A2780 and A2780AD human ovary carcinoma cells (Table 1).…”

High 1,4-syn-induction in the addition of chiral allyltrichlorostannanes to chiral aldehydes

“…13 We next examined the stereochemical impact of both α and β-aldehyde substituents using chiralsyn and anti disubstituted α-methyl-β-alkoxy aldehydes. [13][14][15] Achiral allyltrichlorostannane 4 reacted with chiral syn-α,β-disubstituted 14 aldehyde 14 to give the corresponding 1,2-syn-1,3-syn product 15 in 92% yield and with 96:04 diastereoselectivity (Scheme 6). This example shows that a 1,2-syn aldehyde has a preference to give the product with Felkin addition as well as 1,3-syn addition.…”

“…Another possibility to consider in these reactions is that nonbonded interactions between the allyltrichlorostannane and aldehyde α substituents may not be significant in pericyclic transition states leading to either Felkin or anti-Felkin addition products. [13][14][15][16][17] Allyltrichlorostannane additions to α-aminoaldehydes In recent years there has been a major research effort towards the development of clinically useful inhibitors of aspartyl proteases. [18][19][20][21] This worldwide search has led to various peptide isosteres, wherein the scissile peptide bond is replaced by a hydrolytically more stable isosteric functional group.…”

Aldol reactions

“…(25) 50 Nestes sistemas catalíticos, quando se emprega a oxazolidinona como auxiliar quiral, obtém-se um dos adutos anti, enquanto que o aduto anti de configuração oposta pode ser acessado com o auxiliar de Crimmins (Esquema 23). 51 A adição dos haletos de magnésio torna-se complementar aos sistemas tradicionais de Evans ou Crimmins. Esse sistema reduz o custo da enolização: não há pré-formação de enolatos, ao mesmo tempo que fornece um novo processo de obtenção de aldóis anti por meio de auxiliares quirais.…”