Lithiated 3-tosylpropanal and 4-tosyl-2-butanone dimethyl acetals as β-acylvinyl anion equivalents for the synthesis of unsaturated 1,4-dicarbonyl compounds and α,β-butenolides

Synthesis facilitates an understanding of the structural basis for translation inhibition by the lissoclimides

The lissoclimides are unusual succinimide-containing labdane diterpenoids that were reported to be potent cytotoxins. Our short semisynthesis and analogue-oriented synthesis approaches provide a series of lissoclimide natural products and analogues that expand the structure-activity relationships (SARs) in this family. The semisynthesis approach yielded significant quantities of chlorolissoclimide (CL) to permit an evaluation against the National Cancer Institute's 60-cell line panel and allowed us to obtain an X-ray co-crystal structure of the synthetic secondary metabolite with the eukaryotic 80S ribosome. Although it shares a binding site with other imide-based natural product translation inhibitors, CL engages in a particularly interesting and novel face-on halogen-π interaction between the ligand's alkyl chloride and a guanine residue. Our analogue-oriented synthesis provides many more lissoclimide compounds, which were tested against aggressive human cancer cell lines and for protein synthesis inhibitory activity. Finally, computational modelling was used to explain the SARs of certain key compounds and set the stage for the structure-guided design of better translation inhibitors.

Synthesis of γ-keto sulfones by copper-catalyzed oxidative sulfonylation of tertiary cyclopropanols

Preparation of γ-keto sulfones via ring-opening sulfonylation of cyclopropanols.

Efficient Synthesis of the Odourant, 2-Nonen-4-Olide

A three-step synthesis of 2-nonen-4-olide starting from heptanal is reported. (E)-3-Nonenoic acid, prepared by Knoevenagel condensation of malonic acid and heptanal, was oxidised by performic acid, a process accompanied by lactonisation, to give 3-hydroxynonan-4-olide in 85% yield. This lactone when reacted with MsCl in the presence of Et3N gave, by elimination, 2-nonen-4-olide in 88% yield. The overall yield was 75%. The odour of the product was evaluated by GC-olfactory analysis and sniffing blotter confirming an oily, coconut-like, and rancid odour.

Zinc carbenoid-mediated chain extension: preparation of alpha,beta-unsaturated-gamma-keto esters and amides

An efficient one-pot preparation of alpha,beta-unsaturated-gamma-keto esters and amides has been developed. A zinc carbenoid-mediated chain extension of a beta-dicarbonyl substrate provides access to an intermediate zinc enolate, which is treated sequentially with a halogen and amine base. This method has been applied to a variety of ester and amide starting materials, as well as to amino acid-derived substrates and to a formal synthesis of (R,R)-(-)-pyrenophorin.

A mild, catalytic, and highly selective method for the oxidation of alpha,beta-enones to 1,4-enediones

A new and simple method is described for the one-step oxidation of alpha,beta-enones to 1,4-enediones in good yields (generally 80-90%) using t-butylhydroperoxide as stoichiometric oxidant and 20% Pd(OH)2 on carbon (5 mol %) as catalyst in CH2Cl2 solution. The same reagents have been used to convert ethylene ketals of alpha,beta-enones to the corresponding monoethylene ketals of 1,4-enediones. Seven representative examples are presented in Table 1. All of the available evidence on these oxidations points to a radical-chain mechanism initiated by the tert-butylperoxy radical (see Scheme 1). gamma-tert-Butylperoxy ethers are formed as major products in the oxidation of alpha,beta-enones possessing only a single gamma-hydrogen.