Patricia Perfetti

Et3B- and Et2Zn-Mediated Radical Additions to Glyoxylate Imines, Compared Stereoinductions

Abstract 1,3-Stereoinduction in the addition of alkyl radicals to glyoxylic imines derived from various chiral amines has been investigated. New synthetic methodologies involving Et 3 B and Et 2 Zn as mediators have been compared. Dihydro-1,4-oxazin-2-one ( 2b ) gave the highest d.e. but no chemoselectivity. Open chain analogues derived from β-alkoxyamines led to good stereoinduction when the reaction was performed with Et 2 Zn which is a bidentate complexing reagent.

A short and efficient synthesis of (−)-Ambrox® from (−)-sclareol using a ruthenium oxide catalyzed key step.

Abstract (−)-Ambrox® 5 has been synthesized in 3 steps from natural (−)-sclareol 1 . Depending on the reoxidizing agents and the reaction conditions used in the ruthenium oxide catalysed key step, overall yields of 79% (NaIO 4 /RuO 4 ) or 48% (Ca(OCl) 2/ RuO 4 -) were observed.

A flexible, stereoselective dimethylzinc-mediated radical-anionic cascade: dramatic influence of additional Lewis acids.

Dimethylzinc-mediated addition of acyloxymethyl radicals to diethyl fumarate led to the highly stereoselective formation of disubstituted gamma-lactones in mean to good yields; this cascade provides a new example of a one-pot process mediated by dimethylzinc involving a tandem radical-anionic reaction; the chemoselectivity of the reaction was totally modified by additional Lewis acids.

Synthesis of norambracetal: A new ambergris derivative.

Abstract We describe the synthesis of norambracetal 14 from sclareol 1 using γ -homobicyclofarnesilic aldehyde1O as a key intermediate.

Synthesis of ambracetal and epi-8-ambracetal

A protection-deprotection sequence is used in order to control the formation of the exocyclic double bond of compound 10 which is further used for the synthesis of the title compounds.

Stereoselective synthesis of racemic α-amino-acid derivatives with a β-lactam skeleton: Application of the Staudinger reaction to chiral imines of methyl glyoxylate

Abstract Selected imines of methyl glyoxylate act as good partners in the Staudinger cycloaddition reaction with a series of substituted ketenes. The cis stereoselectivity is almost complete with electron-donor substituted ketenes, but the asymmetric induction is low when imines derived from chiral 1-aryl-ethylamines are used.

Synthesis of Cαα-unsymmetrically disubstituted nitroesters by electron transfer C-alkylation of ethyl 2-nitropropionate anion

Abstract The ethyl 2-nitropropionate anion was shown to react with six reductive alkylating agents to give new C αα -unsymmetrically disubstituted nitroesters and in some cases new ethyl monosubstituted methacrylates. The C -alkylation was shown to proceed by the S RN 1 mechanism which was confirmed by the classical criteria for S RN 1 reaction: the electron-withdrawing group effect and classical inhibition experiments by dioxygen, p -dinitrobenzene, cupric chloride or TEMPO. For example, ethyl 2-methyl-2-nitro-3- p -nitrophenylpropionate was transformed in the corresponding amino acid.

A new synthetic approach for novel 4-substituted-5-nitroimidazoles

Abstract A new synthetic approach, involving an SRN1 reaction of the anion of 1-methyl-4-phenylsulfonyl-methyl-5-nitro-1H-imidazole with 2,2-dinitropropane and a radical anion or a concerted radical reductive elimination of sulfonyl and nitro groups affords an original 5-nitroimidazole bearing a trisubstituted ethylenic double bond at 4-position.

A short efficient synthesis of ambraketal (four steps) and epiambraketal (five steps) from sclareol

Ambraketal 7 and epiambraketal 8 are synthesized efficiently from sclareol 1. The key intermediate 5 is obtained by a regioselective elimination of ketoacetate 4 resulting from the side chain oxidative degradation of 1 by ruthenium tetroxide generated in situ.

Diastereoselective synthesis of a methylated derivative of phomozin a phytotoxin isolated from Phomopsis helianthi, a phytopathogenic fungus of sunflowers

Abstract A methylated derivative of the phytotoxin phomozin ( 2 ) is synthesized in high yield via the regioselective coupling of 2-methyl-4-benzyl orsellinic acid ( 6 ) and ( R * , R * ) benzyl dimethylglycerate ( 9 ) and one step hydrogenolysis of the benzyl and benzoyl protection.