Tomas Hudlicky

Selective reduction of α,β-unsaturated esters in the presence of olefins

Abstract Several α,β-unsaturated esters containing also isolated olefins or other functionalities subject to saturation were selectively reduced to the corresponding saturated esters by magnesium in methanol.

Morphine Synthesis and Biosynthesis-An Update

Bennett H. Novak1, Tomas Hudlicky* 1, Josephine W. Reed1, Johann Mulzer*2 and Dirk Trauner2 1Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA 2Institut fur Organische Chemie der Universitat Wien, Wahringerstrase 38 A-1090 Vienna, Austria Abstract: This review covers recent developments in the area of morphine synthesis and biosynthesis. Literature is reviewed since the publication of the last major review. The first part of the chapter discusses recent advancements in biosynthesis of morphine alkaloids. Total syntheses published since 1996 are reviewed next and the third section discusses all published approaches to morphine skeleton. At the end of the of the chapter, an additional reference list is provided for synthesis of medicinally important derivatives, improvements in alkoloid interconversion, as well as a list of all dissertations dealing with morphine synthesis.

Completion of the seven-step pathway from tabersonine to the anticancer drug precursor vindoline and its assembly in yeast

Significance Bioinformatics and virus-induced gene silencing (VIGS)-guided gene discovery combined with biochemical enzyme assays show that tabersonine 3-oxygenase (T3O) and tabersonine 3-reductase (T3R) are required to form 3-hydroxy-16-methoxy-2,3-dihydrotabersonine, an intermediate in the formation of anticancer drug precursor vindoline from tabersonine. In the absence of T3R, tabersonine is converted by T3O to a series of byproducts that can no longer be used by T3R, suggesting a concerted reaction mechanism. Engineering the seven-gene pathway in yeast demonstrated a prototype platform of high potential for industrial production of the anticancer drug precursor vindoline. Antitumor substances related to vinblastine and vincristine are exclusively found in the Catharanthus roseus (Madagascar periwinkle), a member of the Apocynaceae plant family, and continue to be extensively used in cancer chemotherapy. Although in high demand, these valuable compounds only accumulate in trace amounts in C. roseus leaves. Vinblastine and vincristine are condensed from the monoterpenoid indole alkaloid (MIA) precursors catharanthine and vindoline. Although catharanthine biosynthesis remains poorly characterized, the biosynthesis of vindoline from the MIA precursor tabersonine is well understood at the molecular and biochemical levels. This study uses virus-induced gene silencing (VIGS) to identify a cytochrome P450 [CYP71D1V2; tabersonine 3-oxygenase (T3O)] and an alcohol dehydrogenase [ADHL1; tabersonine 3-reductase (T3R)] as candidate genes involved in the conversion of tabersonine or 16-methoxytabersonine to 3-hydroxy-2,3-dihydrotabersonine or 3-hydroxy-16-methoxy-2,3-dihydrotabersonine, which are intermediates in the vindorosine and vindoline pathways, respectively. Biochemical assays with recombinant enzymes confirm that product formation is only possible by the coupled action of T3O and T3R, as the reaction product of T3O is an epoxide that is not used as a substrate by T3R. The T3O and T3R transcripts were identified in a C. roseus database representing genes preferentially expressed in leaf epidermis and suggest that the subsequent reaction products are transported from the leaf epidermis to specialized leaf mesophyll idioblast and laticifer cells to complete the biosynthesis of these MIAs. With these two genes, the complete seven-gene pathway was engineered in yeast to produce vindoline from tabersonine.

Symmetry‐Based Design for the Chemoenzymatic Synthesis of Oseltamivir (Tamiflu) from Ethyl Benzoate

A short chemoenzymatic formal synthesis of oseltamivir from ethyl benzoate has been achieved. The key steps involve a toluene dioxygenase-mediated dihydroxylation, hetero-Diels-Alder cycloaddition, and generation of C4 acetamido functionality. The formal synthesis of oseltamivir is achieved in ten steps and incorporates a unique translocation of the olefin with concomitant elimination of the C2 hydroxy group (see scheme).

Microbial oxidation of aromatics in enantiocontrolled synthesis. 2. Rational design of aza sugars (endo-nitrogenous). Total synthesis of +-kifunensine, mannojirimycin, and other glycosidase inhibitors.

A general method of synthesis for lactones and lactams related to carbohydrates has been developed that relies on the biocatalyticgeneration of 1-chloro-2,3-dihydroxycyclohexa-4,6-diene (l), obtained in excellent yield by fermentation of chlorobenzene with Pseudomonasputida 39D, followed by further functionalization to nitrogen-substituted cyclitols. These amino or azido cyclitols of type 15 are then subjected to controlled ozonolysis, which yields either lactones such as 27 or lactams containing five-membered (28) or six-membered (20 and 23) rings. Such compounds are useful intermediates for the preparation of aza sugars. Mannojirimycin (84 has been synthesized in seven steps from chlorobenzene. Kifunensine (7) has been prepared in 11 steps from chlorobenzene following an intersection with Hashimotos procedure. Full experimental and spectral details are provided for all compounds. The potential of this general method and implications of the disclosed design features in the field of amino sugar and aza sugar synthesis are indicated.

Molecular Properties of the “ideal” Inhaled Anesthetic: Studies of Fluorinated Methanes, Ethanes, Propanes, and Butanes

We examined 35 unfluorinated, partially fluorinated, and perfluorinated methanes, ethanes, propanes, and butanes to define those molecular properties that best correlated with optimum solubility (low) and potency (high). Limited additional data were obtained on longer-chained alkanes. Using standard techniques, we assessed anesthetic potency (minimum alveolar anesthetic concentration [MAC] in rats); vapor pressure; stability in soda lime; and solubility in saline, human blood, and oil. If nonflammability, stability, low solubility in blood, clinically useful vapor pressures, and potency permitting delivery of high concentrations of oxygen are essential components of an anesthetic that might supplant those presently available, our data indicate that such a drug would have three or four carbon atoms with single or dual hydrogenation of two carbons, especially terminal carbons. We conclude that: 1) smaller and larger molecules and lesser hydrogenation provide insufficient potency; 2) high vapor pressures of smaller molecules do not permit the use of variable bypass vaporizers; 3) greater hydrogenation enhances flammability, and complete hydrogenation decreases potency; 4) internal hydrogenation decreases stability; and 5) greater hydrogenation increases blood solubility.

A short chemoenzymatic synthesis of (+)-narciclasine

Abstract The title alkaloid has been synthesized in eight operations from dibromobenzene and o -vanillin, via enzymatic oxidation of the former compound, Suzuki coupling and a Bischler-Napieralski type cyclization as the key transformations.

Stereospecific synthesis of aminocyclitols via cycloadditions of unsymmetrical, optically pure dienes : conduramine A-1 and dihydroconduramine A-1

Stereospecific synthesis of Conduramine A-1 and Dihydroconduramine A-1 has been achieved by a fully regio- and stereospecific hetero Diels-Alder cycloaddition of a nitrosyl derivative and homochiral 1-halocyclohexadiene diols obtained by microbial oxidation of halobenzenes.

Synthesis of morphine alkaloids and derivatives.

This review summarizes recent developments in the total synthesis of morphine alkaloids and some of the semisynthetic derivatives. The literature is covered for the period of 5 years after the publication of the last review in 2005. The syntheses that appeared in this period are covered in detail and are placed in the context of all syntheses of opiate alkaloids since the original one published by Gates in 1952. The introduction covers the historical aspects of total synthesis of these alkaloids. The synthesis of some of the medicinally useful derivatives is reviewed in the last section along with some of the methodology required for their preparation.

Toward a ‘reagent-free’ synthesis

Several synthetic pathways to cyclohex-5-ene-1R,2S,3R,4R-tetrol (conduritol C) and cyclohex-5-ene-1S,2R,3R,4R-tetrol (conduritol F) are compared; each is analyzed for effectiveness of waste minimization. The latest synthesis, reported in this manuscript, combines enzymatic transformations with electrochemical methods. The concept of “effective mass yield” (EMY) is defined and illustrated.