A Diels-Alder Route to Angularly Functionalized Bicyclic Structures.

A Diels-Alder based route to trans-fused angularly functionalized bicyclic structures has been developed. This transformation features the use of a tetrasubstituted dienophile in the cycloaddition step.

Origins of stereoselectivity in the trans Diels-Alder paradigm.

The regioselectivity and stereoselectivity aspects of the Diels-Alder/radical hydrodenitration reaction sequence leading to trans-fused ring systems have been investigated with density functional calculations. A continuum of transition structures representing Diels-Alder and hetero-Diels-Alder cycloadditions as well as a sigmatropic rearrangement have been located, and they all lie very close in energy on the potential energy surface. All three pathways are found to be important in the formation of the Diels-Alder adduct. Reported regioselectivities are reproduced by the calculations. The stereoselectivity of radical hydrodenitration of the cis-Diels-Alder adduct is found to be related to the relative conformational stabilities of bicyclic radical intermediates. Overall, the computations provide understanding of the regioselectivities and stereoselectivities of the trans-Diels-Alder paradigm.

An Ionic Diels-Alder Route to cis-Fused Octalins Containing an All-Carbon Quaternary Stereocenter in an Angular Position.

We describe herein the development of efficient and stereoselective synthetic routes to a series of cis-octalins possessing an all-carbon quaternary center in an angular position.

Improved dienophilicity of nitrocycloalkenes: prospects for the development of a trans-Diels-Alder paradigm.

The development of an efficient and stereoselective trans-Diels-Alder paradigm is described. A central element of this transformation is the introduction of a temporary dienophilic functionality (A), which serves both to activate the substrate for Diels-Alder cycloaddtion and, through its subsequent removal, to facilitate conversion of the cis-fused cycloadducts to the trans-fused series.

On the emerging role of chemistry in the fashioning of biologics: synthesis of a bidomainal fucosyl GM1-based vaccine for the treatment of small cell lung cancer.

The synthesis of the novel small cell lung cancer (SCLC) fucosyl GM1-based vaccine construct, featuring insertion of the HLA-DR binding 15 amino acid sequence derived from Plasmodium falciparum, is described. The resultant glycopeptide has been synthesized in an efficient manner. Finally, successful conjugation of the glycopeptide to the keyhole limpet hemocyanin (KLH) carrier protein completed the preparation of the vaccine.

Concise Synthesis of the Xenibellols Core.

We describe herein a concise synthesis of an intermediate, via 2,3-Wittig rearrangement and Williamson etherification, en route to the natural products, xenibellols A and B.

Syntheses of Isomerically Pure Reference Octalins and Hydrindanes.

We describe herein the development of efficient and stereoselective synthetic routes to a range of cis- and trans- octalin and hydrindane target compounds.

Feigrisolide C: structural revision and synthesis.

[Carbohydrate structure: see text] The original macrodiolide structure proposed for feigrisolide C was incorrect. The true structure of feigrisolide C was identified as (2'S,3'S,6'R,8'R)-homononactoyl (2R,3R,6S,8S)-nonactic acid, which was confirmed by total synthesis.

Synthesis of the proposed structure of feigrisolide C.

[reaction: see text] Possible structures of feigrisolide C were synthesized via ring-closing olefin metathesis reaction of a diester derivative prepared from 8-epi-nonactic acid, but physical characteristics of the synthetic samples did not match with those of the natural sample of feigrisolide C.