65518-46-9

Chiral pyridinium phosphoramide 1·HX was designed to be a new class of chiral Br?nsted acid catalyst in which both the pyridinium proton and the adjacent imide-like proton activated by the electron-withdrawing pyridinium moiety could work cooperatively as strong dual proton donors. The potential of 1·HX was shown in the enantioselective Diels-Alder reactions of 1-amino dienes with various dienophiles including N-unsubstituted maleimide, which has yet to be successfully used in an asymmetric Diels-Alder reaction.

Pseurotins comprise a family of structurally related Aspergillal natural products having interesting bioactivity. However, little is known about the biosynthetic steps involved in the formation of their complex chemical features. Systematic deletion of the pseurotin biosynthetic genes in A. fumigatus and invivo and invitro characterization of the tailoring enzymes to determine the biosynthetic intermediates, and the gene products responsible for the formation of each intermediate, are described. Thus, the main biosynthetic steps leading to the formation of pseurotinA from the predominant precursor, azaspirene, were elucidated. The study revealed the combinatorial nature of the biosynthesis of the pseurotin family of compounds and the intermediates. Most interestingly, we report the first identification of an epoxidase C-methyltransferase bifunctional fusion protein PsoF which appears to methylate the nascent polyketide backbone carbon atom in trans. A maze: Pseurotins are a family of structurally related bioactive natural products from Aspergilli. Through genetic and biochemical studies, the biosynthetic pathway for the formation of azaspirene, synerazol, and pseurotin A/D have been elucidated, and reveal the combinatorial nature of their biosyntheses. PsoF was identified as bifunctional epoxidase methyltransferase enzyme, thus providing the first example of a trans-acting polyketide C-methyltransferase.

As an approach to the synthesis of amiclenomycin (1), we describe here the synthesis of a 1-aminocyclohexa-2,5-diene moiety. The cis isomer 2 was obtained by means of a Diels - Alder reaction between trans-1,2-bis(phenylsulfonyl)ethylene and N-(allyloxyca

The cationic palladium(II) aquo hydride, trans-(Cy3P)2Pd(H)(H2O)(+)BF4(-), is an excellent catalyst for the carbonylation of alkynols to dienoic acids and esters and of alkynediols to cross-conjugated diesters.

A simple and general benzocyclization sequence, useful in the conversion of α-methylene ketones/aldehydes 1a-f to phenolic acetates 6a-g via the dienoic acids 5a-g is presented.The technique has provided a new route to the terpenoids, thymol acetate (6f) and (R)-(-)-curcuphenol acetate (6g).