Aurelio Ortiz

Secondary metabolites of soil Bacillus spp.

Bacillus species produce secondary metabolites that are the object of natural product chemistry studies. The wide structural variability of these compounds has attracted the curiosity of chemists and their biological activities have inspired the pharmaceutical industry to search for lead structures in microbial extracts. Screening of microbial extracts reveals the large structural diversity of natural compounds with broad biological activities, such as antimicrobial, antiviral, immunosuppressive, and antitumor activities, that enable the bacterium to survive in its natural environment. These findings widen the potential industrial importance of Bacillus spp., particularly of B. thuringiensis, beyond insecticidal usage and may help explain the role of Bacillus spp. in the soil ecosystem.

(S)-4-Isopropyl-5,5-dimethyl-1,3-oxazolidinethione as chiral auxiliary for the intramolecular sulfur transfer in α,β-unsaturated N-acylimides, promoted by NbCl5

Abstract The 1,3-oxazolidinethione 4 has been synthesized from ( S )-valine and used in the intramolecular sulfur transfer in its N -enoyl derivatives in the presence of NbCl 5 as catalyst, which, moreover, works as an indicator of the course of the reaction. The adducts have subsequently been transformed into the corresponding β-mercapto esters by action of Sm(OTf) 3 in methanol.

A new method for the preparation of unsymmetrical 1,4-substituted piperazine derivatives

Abstract Symmetrical and unsymmetrical N , N ′-piperazine derivatives of (−)-norephedrine and o -aminophenol were synthesized stereoselectively in yields >70% by reduction of the corresponding N , N ′-ethylenebisoxazolidine heterocycles. The stereochemistry at the ring fusion carbons was established by NMR spectroscopy and X-ray crystallography.

The synthetic versatility of oxazolidinethiones

Different methods for the preparation of oxazolidinethiones and their more recent applications are reviewed. In this review, novel rearrangements and new reactions have also been summarized which for their homologous oxazolidinones have not been observed. The principal application of oxazolidinethiones has been as chiral auxiliaries in asymmetric aldol addition reactions for the obtention of chiral fragments containing one or two stereogenic centres with the stereochemistry required for the preparation of complex natural products.

One Step Syntheses of Heteropropellanes

Abstract The preparation of two new propellanes containing the oxazino-oxazine moiety is described. The structure of 2,7-dioxa-5,10-diaza[4.4.4] propellane was determined by X-ray crystallographic analysis

HIGHLY REGIO- AND STEREOSELECTIVE FORMATION OF 2-HYDROXY-5,6-DIHYDRO-2H-1,4-OXAZINES. AN X-RAY AND 13C NMR STUDY

Abstract (−)-Norephedrine and (−)-norpseudoephedrine undergo condensation with a wide variety of 1,2-diketones to yield the corresponding 2-hydroxy-5,6-dihydro-2H-1,4-oxazines with high regio- and stereoselectivity. The X-ray structure analysis of five of the compounds studied shows that the stereochemistry at the newly formed stereogenic center is S in all cases.

Genetic manipulation in Bacillus thuringiensis for strain improvement

Bacillus thuringiensis (Bt) has been used as a biopesticide in agriculture, forestry and mosquito control because of its advantages of specific toxicity against target insects, lack of polluting residues and safety to non-target organisms. The insecticidal properties of this bacterium are due to insecticidal proteins produced during sporulation. Despite these ecological benefits, the use of Bt biopesticides has lagged behind the synthetic chemicals. Genetic improvement of Bt natural strains, in particular Bt recombination, offers a promising means of improving efficacy and cost-effectiveness of Bt-based bioinsecticide products to develop new biotechnological applications.

An Ultra-Violet Tolerant Wild-Type Strain of Melanin-Producing Bacillus thuringiensis

Background: Bacillus thuringiensis is the most successful biological control agent used in agriculture, forestry and mosquito control. However, the insecticidal activity of the B. thuringiensis formulation is not very stable and rapidly loses its biological activity under field conditions, due to the ultraviolet radiation in sunlight. Melanin is known to absorb radiation therefore photo protection of B. thuringiensis based on melanin has been extensively studied. Objectives: The aim of this study was to find a wild type strain of naturally melanin-producing B. thuringiensis to avoid any mutation or manipulation that can affect the Cry protein content. Materials and Methods: Bacillus thuringiensis strains were isolated from soils of different States of Mexico and pigment extraction was followed by lowering the pH to 2 using 1N HCl. Pigment was characterized by some chemical tests based on its solubility, bleaching by H2O2 and flocculation with FeCl3, and using an Infrared (IR) spectrum. Ultraviolet (UV) irradiation experiment was performed to probe the melanin efficacy. Results: ELI52 strain of B. thuringiensis was confirmed to naturally produce melanin. The Cry protein analysis suggested that ELI52 is probably a B. thuringiensis subsp. israelensis strain with toxic activity against the Diptera order of insects. Ultra Violet protection efficacy of melanin was probed counting total viable colonies after UV radiation and comparing the results with the non-producing melanin strain L-DOPA (L-3, 4-dihydroxyphenylalanine) was also detected in the culture. ELI52 strain showed an antagonistic effect over some common bacteria from the environment. Conclusions: ELI52 wild-type strain of B. thuringiensis is a good bio-insecticide that produces melanin with UV-resistance that is probably toxic against the Diptera order of insects and can inhibit the growth of other environmental bacteria.

Syntheses of Bisoxazolidines and Morpholones

Abstract The preparation of two new bisoxazolidines, two N-(2-hydroxyethyl)- N-alkylglycine derivatives and two morpholones is described. The structure of (5S, 6R)-N-isopropyl-5-methyl-6-phenyl-l, 4-oxazin-2-one was established by X-ray crystallographic analysis. Supplementary Material available: Tables of atomic coordinates, thermal parameters, bond lengths and angles and observed and calculated structure factors have been deposited at the Cambridge Crystallographic Data Center.

A novel nucleophilic attack to N-enoyl oxazolidinethiones

Abstract The oxazolidinethione synthon can act as a chiral auxiliary and nucleophile (S−) carrier molecule simultaneously. Surprisingly, the thiolate attacks N-enoyl oxazolidinethiones producing a new heterocycle, as established by X-ray analysis.