Chemoselective and stereoselective lithium carbenoid mediated cyclopropanation of acyclic allylic alcohols

A new method for the chemo- and stereoselective conversion of acyclic allylic alcohols into the corresponding substituted cyclopropane derivatives has been developed using lithium carbenoids.

Titanium carbenoid-mediated cyclopropanation of allylic alcohols: selectivity and mechanism

A new method for the chemo- and stereoselective conversion of allylic alcohols into the corresponding cyclopropane derivatives has been developed. The cyclopropanation reaction was carried out with an unprecedented titanium carbenoid generated in situ from Nugent's reagent, manganese and methylene diiodide. The reaction involving the participation of an allylic hydroxyl group, proceeded with conservation of the alkene geometry and in a high diastereomeric excess. The scope, limitations and mechanism of this metal-catalysed reaction are discussed.

The synthesis of 3-hydroxy-2,4,8-trimethyldec-8-enolides and an approach to 3,4-dihydroxy-2,4,6,8-tetramethyldec-8-enolide

The synthesis of several derivatives of 3-hydroxy-2,4,8-trimethyldec-8-enolide and attempts at the synthesis of 3,4-dihydroxy-2,4,6,8-tetramethyldec-8-enolide (1), a structure which has been assigned to a metabolite of the phytopathogenic fungus, Botrytis cinerea, gave products whose spectroscopic data had significant differences from those reported for the natural product 1. The rare 11-membered lactone rings were constructed by ring-closing metathesis reactions. The increase in conformational restrictions imposed by the substituents has a high influence on the stereochemistry of the ring-closing metathesis reaction and gives rise to a decrease in the yield for the synthesis of 11-membered lactones. The predominant alkene which was obtained was the (Z)-isomer. The observed spectroscopic differences between the synthesized lactones and the natural product and the spectroscopic data of its acetylated derivative 26a allowed us to revise the structure 1 to that of the γ-butyrolactone 26.

Exploring mutasynthesis to increase structural diversity in the synthesis of highly oxygenated polyketide lactones

Four new highly oxygenated 11-membered lactones (11–14) were synthesized by a combination of metabolic engineering techniques with complex chemical substrate synthesis.

The putative role of botrydial and related metabolites in the infection mechanism of Botrytis cinerea

Phytotoxic assays, performed both in vitro and in vivo on leaves of Phaseolus vulgaris, with metabolites excreted by the fungus B. cinerea are evaluated. Exogenous application of the phytotoxin botrydial has been found to produce severe chlorosis and cell collapse and facilitated fungal penetration and colonization of plant tissue. The results also show a light-dependent action mechanism for the phytotoxin and seem to indicate that botrydial is a non-host-specific toxin involved in fungal infection of B. cinerea.

Botrydial is produced in plant tissues infected by Botrytis cinerea

The fungal metabolite botrydial was detected for the first time in ripe fruits of sweet pepper (Capsicum annuum) wound-inoculated with conidial suspensions of Botrytis cinerea and also in leaves of Phaseolus vulgaris and Arabidopsis thaliana inoculated without wounding. This phytotoxin was produced in soft rot regions of the infection. In C. annuum, the most aggressive isolate produced the highest botrydial concentrations in planta. The levels of botrydial produced by this isolate did not correlate with the reported relative susceptibilities of four P. vulgaris genotypes. The results suggest that botrydial is a pathogenicity factor for this fungus, but not a primary determinant of pathogenicity.

Novel rearrangements of sesquiterpenoid panasinsane derivatives under acidic conditions

The sesquiterpenoid panasinsane derivatives 11 and 14-16 have been prepared from caryophyllene oxide (7). The novel rearrangement reactions of compounds 11 and 14 under TCNE-catalyzed solvolysis conditions and the reactions of compounds 15 and 16 under superacid conditions (HSO3F/Et2O, -63 degrees C) have been investigated. The ginsenol derivative 17 is obtained from compounds 11 and 14 under TCNE-catalyzed conditions. The rearrangement of compounds 15 and 16 under superacid conditions leads to the novel sesquiterpene derivatives (1S,4S,7S,10S,11S)-3,3,10,11-tetramethyltricyclo[5.3.1.0(4,10)]undecan-1,11-yl sulfate (19) and (1S,4S,5S,8S)-2,2,4,8-tetramethyl tricyclo[3.3.2.1(4,8)]undecan-11-one (20). The influence of the secondary hydroxyl group at C-5 of the panasinsane derivatives on the course of these rearrangements is discussed.

[Genetic analysis and relationship to pathogenicity in Botrytis cinerea]

Botrytis cinerea is a plant-pathogenic fungus that produces the disease known as grey mould in a wide variety of agriculturally important hosts in many countries. Ten strains from different locations collected on different years have been isolated and characterized by several methods (morphological, biochemical, genetical and molecular). Results showed that clear morphological differences exist between strains, and showing a relationship between the presence of sclerotia and pathogenicity. The conidial size and the nuclear number were highly variable between different strains. Pulsed-field gel electrophoresis showed a unique karyotype for each strain, highly polymorphic between strains and with a number of bands ranging from 4 to 8. An efficient transformation system has been achieved through the plasmid pAMPF21, containing the region AMA1 of Aspergillus nidulans. Lastly, from a genomic library the gdhA gene has been cloned. This gene produces an RNAm of 1.7 Kb and complements the deficiency on glutamate dehydrogenase activity of A. nidulans.

Secobotrytriendiol and related sesquiterpenoids: new phytotoxic metabolites from Botrytis cinerea

Six new sesquiterpenoid metabolites (1, 3-7) have been isolated from Botrytis cinerea. Their structures were elucidated by means of MS and extensive NMR studies. The phytotoxic activities of these new products have been evaluated.

Biotransformation of (4E,8R)-caryophyll-4(5)-en-8-ol by Botrytis cinerea

Biotransformation of (4E,8R)-caryophyll-4(5)-en-8-ol (1) with Botrytis cinerea afforded 14 products (3-16). Thirteen of these (4-16) are described here for the first time. The main reaction paths involved the isomerization of the double bond at C-4/C-5 and hydroxylation of methyl groups.

Biotransformation of the fungistatic sesquiterpenoid patchoulol by botrytis cinerea

Biotransformation of the fungistatic sesquiterpenoid patchoulol (1) by the fungus Botrytis cinerea affords the 5-, 7- and (8R)-hydroxy (2, 3, and 5) derivatives as the major metabolites, together with a number of minor metabolites (4, 6-9) arising from hydroxylation at C-2, C-3, C-5, C-9, C-13, and C-14.

Biotransformation of caryophyllene oxide by botrytis cinerea

Biotransformation of caryophyllene oxide (1) with B. cinerea afforded 15 products (2-16). Ten of these (3-5, 7, 9-11, and 14-16) are reported here for the first time. The main reaction paths involved stereoselective epoxidation at C-8/C-13 and hydroxylation at C-7. A rearranged compound was found, which was a cyclization product 16 possessing the caryolane skeleton.

The biotransformation of some clovanes by botrytis cinerea

The metabolism of the fungistatic agent 2beta-methoxyclovan-9alpha-ol (2) by the fungus Botrytis cinerea has been investigated. Biotransformation of compound 2 yielded compounds 3-5, 7, and 9. The major metabolites of compound 2 each show much reduced biological activity when compared with the parent compound. Also studied were the effects of B. cinerea on the metabolism of the related compounds 2beta-methoxyclovan-9-one (3), 2beta-methoxyclovan-9beta-ol (4), and clovan-2,9-dione (6). Compounds 3, 4, 8, and 9 are described for the first time.

An autonomously replicating plasmid transforms Botrytis cinerea to phleomycin resistance

A transformation system has been developed for the pathogen fungus Botrytis cinerea, based on the utilization of the wide host plasmid pUT737 that contains the Sh ble gene, conferring resistance to phleomycin. Transformed protoplasts were regenerated at 10-25 micrograms ml(-1) of phleomycin, at a frequency of 25-40 transformants per microgram of DNA, and they were resistant up to 50 micrograms ml(-1). Southern hybridization using undigested and digested total DNA showed the presence of circular autonomously replicating plasmid pUT737 in the transformants. Reisolated plasmid from transformed fungus transformed E. coli and rescued plasmid was identified as PUT737. Transformants were grown for four generations under non-selective conditions and replicative plasmids were still detected. Plasmids present in all transformants at this stage had been modified from native pUT737 and showed the same size and configuration indicating that selection through stabilizing plasmid forms has happened.