F. Pelizzoni

1,3 Dipolar cycloadditions of azomethine ylides with aromatic aldehydes. syntheses of 1-oxapyrrolizidines and 1,3-oxazolidines.

Abstract Substituted 1-oxapyrrolizidines have been synthetized by cycloaddition of azomethine ylides, generated by aldehydes induced decarboxylation of proline, with carbonyl dipolarophyles. The stereochemistry of the cycloadducts indicate that they arise from the stereospecific formation of one isomer of the azomethine ylide.

Reformatsky intermediate. A C-metallated species.

Abstract 13 C-NMR and 1 H-NMR spectra of the Reformatsky reagent from t-butylbr o moacetate, evidence a C-metallated species: within the limits of detectability of the methods, no O-metallated species can be detected in solution.

Cycloartane triterpene glycosides from Astragalus trigonus

Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-beta-xylopyranoside, cycloastragenol-3-O-[alpha-L-arabinopyranosyl(1-->2)-beta-D- xylopyranosyl]- 6-O-beta-D-xylopyranoside and cycloastragenol-3-O-[alpha-L-arabinopyranosyl (1-->2)-beta-D-(3-O-acetyl)-xylopyranosyl]-6-O-beta-D-xylopyranoside.

Biotransformation of styrenes by a Pseudomonas putida

SummaryA strain of Pseudomonas putida was isolated from soil in the presence of α-methylstyrene, as the sole carbon and energy source. The analysis of the oxidation products from culture broth allowed the identification of 2-phenyl-2-propen-1-ol and 1,2-dihydroxy-3-isopropenyl-3-cyclohexene suggesting the existence of different initial steps in the metabolism of α-methylstyrene. The same strain also oxidized styrene and produced by initial oxidation of the aromatic nucleus a compound identified as 1,2-dihydroxy-3-ethenyl-3-cyclohexene.

Bioconversion of substituted naphthalenes to the corresponding 1,2-dihydro-1,2-dihydroxy derivatives. Determination of the regio- and stereochemistry of the oxidation reactions

A mutant (TTC1) derived from Pseudomonas fluorescens N3 has been obtained for use in the bioconversion of several naphthalene derivatives to the corresponding optically active cis-dihydrodiols on a milligrams-to-grams scale. All main compounds have been characterized, their relative and absolute configuration assigned, and their enantiomeric purity determined. The regio- and stereoselectivity of the transformation has been established. The procedure therefore represents a valid method for the convenient preparation of a pool of valuable chiral syntons and auxiliaries.

Alkaloid and lignan constituents of Cinnamosma madagascariensis

Abstract A new lignan glycoside, 5-methoxy-9-β-xylopyranosyl-(-)- isolariciresinol and two indole alkaloids have been characterised from the bark of Cinnamosma madagascariensis .

C-Metallated reformatsky intermediates. Structure and reactivity.

Abstract 13C-NMR analysis of the Reformatsky intermediates from t-b u tyl-α-bromo acetate, t-b u tyl-α-bromo isobutyrate and t-b u tyl-α-bromo pr o pionate have evidenced C-metallated species. Their ability to act as n u cleophilic reagents under mild conditions and their selectivity towards h a logen-and oxygen containing electrophiles is reported.

Production of substituted naphthalene dihydrodiols by engineered Escherichia coli containing the cloned naphthalene 1,2-dioxygenase gene from Pseudomonas fluorescens N3

Naphthalene dioxygenase, a key enzyme in the dihydroxylation of naphthalene, is encoded by the plasmid pN3, responsible for naphthalene metabolism in Pseudomonas fluorescens N3. The naphthalene dioxygenase, including all the sequences for its expression and the regulatory region, has been localized on the 4.3-kb HindIII-ClaI fragment and on the 3.5-kb HindIII fragment of the plasmid pN3, by Southern analysis using as probes nahA and nahR genes, the homologous genes of the plasmid NAH7 from Pseudomonas putida G7. We cloned in Escherichia coli JM109 the dioxygenase gene and its regulatory region and developed an efficient bacterial system inducible by salicylic acid, able to produce dihydrodiols. E. coli containing recombinant plasmids carrying the dioxygenase gene were analysed for their potential as a biocatalytic tool to produce dihydrodiols from different naphthalenes with the substituent on the aromatic ring at the alpha or beta position. The dihydrodiols, identified by HPLC (high-performance liquid chromatography) and 1H-NMR (nuclear magnetic resonance) were produced with yields ranging from 50 to 94%. The degree of bioconversion efficiency depends on the nature and the position of the substituent and indicates the broad substrate specificity of this dioxygenase and its potential for the production of a wide variety of fine chemicals.

New diterpenoids with clerodane skeleton

Abstract The structure of two diterpenoids with clerodane skeleton isolated from bulbs of Annona coriacea have been established as (1) and (2).

Quadranguloside, a cycloartane triterpene glycoside from Passiflora quadrangularis

Abstract Quadranguloside, a new cyclopropane triterpene glycoside was isolated from the methanolic extract of the leaves of Passiflora quadrangularis . Its structure has been established as 9,19-cyclolanost-24 Z -en-3β,21,26-triol-3,26-di- O -gentiobioside on the basis of hydrolysis and spectral evidence.