Alvaro Takeo Omori

Biocatalysis for desymmetrization and resolution of stereocenters beyond the reactive center: How far is far enough?

The kinetic resolution of racemates and desymmetrization are the most common approaches to the preparation of enantiomerically enriched compounds. These procedures allow the access of high valuable, chiral building blocks for many purposes in academic or industrial R&D endeavors. Nevertheless, the scope of stereochemistry recognition in biotransformations usually occurs at the site of the transformation or when it is close to it (not more than 3 bonds). However, there are a growing number of enzymatic transformations which surpass the limits of stereorecognition of remote chiral (or prochiral) centers. In this account, we would like to present some aspects of biocatalyzed remote resolutions and remote desymmetrizations to call attention for these challenging transformations.

Sassafras oil, carrot bits and microwaves: green lessons learned from the formal total synthesis of (−)-talampanel

A formal total synthesis of (−)-talampanel (1), a 2,3-benzodiazepine is described. This work was undertaken to utilize greener reaction conditions. Safrole (a renewable source) was converted to (1) in eight steps, including an enantioselective bioreduction using carrots as the key step. Microwave irradiation was also used to perform three reaction steps.

Redução enzimática do 4-(dimetilamino)benzaldeído com pedaços de cenoura (Daucus carota): um experimento simples na compreensão da biocatálise

The present paper describes a simple, low-costly and environmentally friendly procedure for reduction of 4-(dimethylamino)benzaldehyde using carrot bits in water. This interdisciplinary experiment can be used to introduce the concepts of biocatalysis and green chemistry to undergraduate students.

Recent Syntheses of Frog Alkaloid Epibatidine

Many natives from Amazon use poison secreted by the skin of some colorful frogs (Dendrobatidae) on the tips of their arrows to hunt. This habit has generated interest in the isolation of these toxins. Among the over 500 isolated alkaloids, the most important is undoubtedly (-)-epibatidine. First isolated in 1992, by Daly from Epipedobates tricolor, this compound is highly toxic (LD50 about 0.4 µg per mouse). Most remarkably, its non-opioid analgesic activity was found to be about 200 times stronger than morphine. Due to its scarcity, the limited availability of natural sources, and its intriguing biological activity, more than 100 synthetic routes have been developed since the epibatidine structure was assigned. This review presents the recent formal and total syntheses of epibatidine since the excellent review published in 2002 by Olivo et al.1 Mainly, this review is summarized by the method used to obtain the azabicyclic core.

MÉTODO DE SÍNTESE DE AZIDAS AROMÁTICAS USANDO VINAGRE

The present paper describes a simple and low-cost procedure for preparation of aryl azides from anilines using vinegar as an unusual solvent/reagent. We observed the sequence of diazotation followed by diazo displacement with sodium azide can be carried out in aqueous solution of acetic acid

Studies Toward the Synthesis of Caramboxin Analogues

Intrigued by the recent discovery of caramboxin by Brazilian researchers, we present the results from our studies toward the racemic synthesis of caramboxin analogs through the orthocarboxylation of 3,5-dimethoxy benzyl derivatives. Three different approaches were tested, and the route involving a Vilsmeier-Haack formylation followed by a Lindgren oxidation provide a potential intermediate for the synthesis of several caramboxin analogs.

Tween® 20-Enhanced Bioreduction of Acetophenones Promoted by Daucus carota Root

The effect of surfactants on the bioreduction of acetophenones mediated by carrot (Daucus carota) root was investigated. Among the tested surfactants, Tween® 20 slightly improved the conversion. The amount of surfactant was optimised, and the presented methodology was applied to other substituted acetophenones, which led to the preparation of their respective optically enriched 1-phenylethanols with high conversion levels and high enantioselectivities.

1-Butyl-1-chloro-3-methyl-3H-2,1λ4-benzoxatellurole: crystal structure and Hirshfeld analysis

Two chemically similar molecules comprise the asymmetric unit and these are connected via Te⋯O secondary bonding. The coordination geometry for each molecule is based on an octahedron with the lone-pair of electrons occupying a position opposite to the n-butyl group.