928-39-2

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An ω-transaminase-triggered intramolecular aza-Michael reaction has been employed for the preparation of cyclic β-enaminones in good yield and excellent enantio- and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza-Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, this biocatalytic aza-Michael step was combined with annulation chemistry, affording unique stereo-defined fused alkaloid architectures.

ω-Alkynyl O-tert-butyldiphenylsilyloximes, upon treatment with odorless 4-tert-butylbenzenethiol in the presence of azobisisobutyronitrile (AIBN) in refluxing benzene, underwent addition of a thiyl radical to the alkynyl group followed by radical cyclizat

This invention pertains generally to treating bacterial infections using organic compounds of Formula I. In certain aspects, the invention pertains to treating infections caused by Gram-negative bacteria. (I) wherein X, Y, R1, R2, R3, R4 and R5 and defined herein.

A catalytic enantioselective formal total synthesis of aspergillide B is reported. This linchpin synthesis was enabled by the development of new conditions for Zn-ProPhenol catalyzed asymmetric alkyne addition. This reaction was used in conjunction with ruthenium-catalyzed trans-hydrosilylation to affect the rapid construction of a late-stage synthetic intermediate of aspergillide B to complete a formal synthesis of aspergillide B in a highly efficient manner.

The development of a general and practical zinc-catalyzed enantioselective alkyne addition methodology is reported. The commercially available ProPhenol ligand (1) has facilitated the addition of a wide range of zinc alkynylides to aryl, aliphatic, and α,β-unsaturated aldehydes in high yield and enantioselectivity. New insights into the mechanism of this reaction have resulted in a significant reduction in reagent stoichiometry, enabling the use of precious alkynes and avoiding the use of excess dimethylzinc. The enantioenriched propargylic alcohols from this reaction serve as versatile synthetic intermediates and have enabled efficient syntheses of several complex natural products. A precious few: A general and practical zinc-catalyzed enantioselective alkyne addition methodology is reported (see scheme). New insights into the mechanism of this reaction have resulted in a significant reduction in reagent stoichiometry, enabling the use of precious alkynes and avoiding the use of excess dimethylzinc. This methodology has enabled the efficient synthesis of several complex natural products.

Keto aldehydes were selectively converted to non-conjugated alkynyl ketones possessing an unsubstituted alkyne terminus using one-pot nonaflation - base catalyzed elimination reaction sequences. Consecutive one-pot nonaflation of keto aldehydes with perfluorobutane-1-sulfonyl fluoride and elimination of the nonaflyl group using the P1 phosphazene base resulted in the formation of a terminal CC triple bond with the keto group remaining intact. Careful optimization of the reaction conditions enabled a highly chemoselective conversion of the aldehyde function in the presence of unprotected keto groups exploiting a minor difference in acidity of their α-hydrogen atoms. Scope and limitations of the protocol as well as possible implementation of these substrates in Sonogashira coupling were explored.

Treatment of the α,β-unsaturated selenyl esters 12 and 14 with Bu3SnH-AIBN produces the corresponding 2-cyclohexenones 13 and 15 respectively via presumed α-ketene alkyl radical intermediates, viz. 10. By contrast, the 2,7-diene esters 34 and 39 undergo tandem radical cyclisations producing diquinanes, e.g. 38 (76%), and the corresponding allene-substituted α,β-unsaturated selenyl ester 48 gives the cyclooctadienone 56 on treatment with Bu3SnH-AIBN in refluxing benzene. The selenyl ester 19 derived from chrysanthemic acid produces a mixture of the γ,δ- unsaturated aldehyde 22 and the corresponding dimer 25a on treatment with Bu3SnH-AIBN. Furthermore, in the presence of methanol the only product from this reaction was the bis(methyl ester) dimer 25b, thereby lending further credence to the involvement of ketene alkyl radical intermediates in these reactions, and in the aforementioned reactions involving 2,6- and 2,7-diene selenyl esters. Treatment of the cyclopropane selenyl esters 59 and 61, containing keto- and oxy-group functionality in their side-chains, with Bu3SnH-AIBN led to excellent syntheses of the enol lactone 66 (76%) and the trans-fused bicyclo[6.1.0]nonane 67 (80-95%) respectively.

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Brefeldin-A, an antiobiotic fungal metabolite, has been obtained in both racemic and natural forms through a direct approach that employs norbornenone and 6-heptyn-2-ol as the basic starting materials.