Giancarlo Jommi

Secoiridoids from Olea europaea

Abstract Three new secoiridoids have been isolated from the leaves of Olea europaea along with the previously reported. The compounds were identified by spectral means.

Sesquiterpenoids of Cinnamosma fragrans baillon: Structure of cinnamolide, cinnamosmolide and cinnamodial

Abstract The constitution and absolute stereochemistry of three new sesquiterpenoid lactons with drimane skeleton have been elucidated by correlating them to confertifolin.

Asymmetric Synthesis of Diethyl α-Amino-α-Alkyl-Phosphonates by Alkylation of the Chiral Schiff Base Derived from (+)-Ketopinic Acid and Diethylaminomethyl Phosphonate

Abstract The alkylation of the chiral Schiff base derived from the condensation of (+)-ketopinic acid and diethyl aminomethylphosphonate followed by hydrolysis affords diethyl (S)-α-amino-α-alkyl phosphonates with high enantiomeric excesses when benzyl or allyl halides are used in the alkylation step. An improved procedure for the preparation of diethyl aminomethylphosphonate is also reported.

Structure and absolute stereochemistry of vanillosmin, a guaianolide from Vanillosmopsis erythropappa

Abstract The structure and absolute stereochemistry of vanillosmin were established by chemical and spectral evidence and by comparison with O -acetyl-isophoto-α-santonic lactone and tetrahydroartabsin “C”.

Sesquiterpenoids of Cinnamosma fragrans baillon: Structure of bemarivolide, bemadienolide and fragrolide

Abstract Structures I, IX and XII have been assigned respectively to bemarivolide, bemadienolide and fragrolide, three new sesquiterpenoid lactones with the drimane skeleton. Some aspects of the reactivity of this class of compounds are discussed.

Metal-directed asymmetric synthesis of diastereoisomeric β-phenyl serines using (+)-ketopinic acid as a chiral auxiliary.

Abstract A new method for the asymmetric synthesis of threo and erythro β-phenylserines using (+)-ketopinic acid as a chiral auxiliary is reported. The reaction was based on the condensation of benzaldehyde with the metal (Li+, K+ or Zn++, enolates of the chiral imines 3 .

Alkylation of chiral phosphonoglycine equivalents: Asymmetric synthesis of diethyl α-amino-α-alkyl-phosphonates

Abstract A model was developed to rationalize the experimental results of the alkylation of chiral phosphonoglycine equivalents yielding α-amino-α-alkyl-phosphonates. The model studies, carried out using semiempirical calculations, have emphasized the role of the chelating effects in influencing the diastereoselectivity of the alkylation step. Chelation can be optimized by tuning the functionality of the substituent at carbon C-1 of the camphor skeleton. By employing 2d , as suggested by the modelling, a major improvement in the enantiomeric excesses of compounds 5 (R=CH 3 , C 2 H 5 ) was obtained.

Asymmetric synthesis of diethyl α-amino α-alkyl-phosphonates by alkylation of chiral phosphonoglycine equivalents : role of chelating effects

Abstract Diethyl α-amino-α-alkyl-phosphonates are obtained in good to high enantiomeric excesses by alkylation of chiral phosphonoglycine equivalents embodying the camphor skeleton. The chelating effects in the alkylation step play an important role in enhancing the diastereoselectivity of the reaction as substantiated by semiempirical calculations (AM1).

Studies toward a model for predicting the diastereoselectivity in the electrophilic amination of chiral 1,3,2-oxazaphospholanes

Abstract A model has been developed for predicting the diastereoselectivity in the electrophilic amination of chiral 1,3,2-oxazaphospholanes derived from ephedrine and pseudoephedrine derivatives. The influence of the five-membered ring conformations and of the bulkiness of the ring substitutents has been deeply analyzed both for reactivity prediction and for 1 H-NMR data interpretation. The theoretical and experimental results are in good agreement.

Stereochemistry of the enzymic 3-hydroxylation of 1,3-dihydro-2H-1,4-benzodiazepin-2-ones

The enzymic hydroxylation at C-3 of demethyldiazepam (1) and diazepam (2) proceeds through stereospecific removal of the pro-S hydrogen atom.