Jean-Pierre Zahra

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.

Synthesis of water-soluble ligands with a quaternary ammonium salt: use in bdphasic palladium-catalyzed telomerisation of butadiene and isoprene

Abstract Water-soluble ligands are synthesized by quaternization of tertiary aminophosphine with either hydrochloric acid or methyl iodide. The use of these ligands in the biphasic palladium-catalyzed telomerisation of butadiene, produces 1-methoxy-2,7-octadiene with 78% selectivity and conversions ranging from 52 to 79%. Conversion and selectivity are little altered on catalyst recycling. Telomerisation of isoprene is somewhat less satisfactory, with a conversion not higher than 52%.

Reductive coupling of α,β-enones I: Reduction of methyl-vinyl ketone and mesityl oxide.

Abstract Reductive coupling of methyl-vinyl ketone with TiCl 4 -Mg gives pinacol 1 (25%). According to the reducing agents, mesityl oxide yields 2,4,5,7-tetramethyl-octa-2,4,6-triene 3 (with 4TiCl 3 -LialH 4 ), triene 3 or 2,4,5,7-tetramethyl-octa-2,6-dien-4,5-diol 5 (with TiCl 4 -Mg), pinacol 5 (with VCl 3 -Mg), and 2-acetyl-1,3,3,4,4-pentamethyl-cyclopentane 7 (with CrCl 3 -Mg or FeCl 3 -Mg or ZrCl 4 or ZrCl 4 -Mg) as major products.

Conjugate addition of allylsilanes to α,β-enones. Obtention of cyclobutyl derivatives

Abstract By conjugate addition of allylsilanes to α,β-enones, cyclobutyl derivatives are formed.

Dammarane derivatives in the fruit lipids of Olea madagascariensis

Abstract The neutral lipids of the fruits (pulp and kernel) of Olea madagascariensis contain about 10% of unsaponifiable matter. Twenty-six 4-demethylsterols and 4,4-dimethylsterols were identified. Among them two compounds, (20S)-5α-dammar-24-en-3β, 20-diol and 5α-dammara-20(21), 24-dien-3β-ol, represent 3.3 and 3.2% of the neutral lipids, respectively. The assigned structures of the two main components are based upon GC retention times, 1H and 13C NMR, and mass spectrometry.

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.

Ethylenic acyl cyanides II: Conjugate addition of alkynylsilanes to ethylenic acyl cyanides.

Abstract 3-Alkynylacyl cyanides or 3-alkynylacids and their esters can be obtained by a conjugate addition of alkynylsilanes to α,β-ethylenic acyl cyanides.

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.

Carbonylation of (+)-2-carene induced by iron-pentacarbonyl

Abstract (+)-2-carene heated neat with iron pentacarbonyl leads to α-phellandrene-Fe(CO) 3 complex ( ∼15 % ), p. cymene ( ∼15 % ), (-)-(1S)-3,8,8-trimethylbicyclo (4.1.1) oct-3-ene-7-one ( ∼50 % ) and (+)-(1S,7S)-3,8,8-trimethylbicyclo (4.1.1.) oct-3-ene-7-ol ( ∼20 % ).

Synthesis of nor-norambracetal

Abstract We describe the synthesis of nor-norambracetal 13 from sclareol 1 , using γ-homobicyclo-farnesylic alcohol 3 as a key intermediate.