Enantioselective Cycloaddition of Formed aza-Dienes and Vinyl Diazo Compounds for the Synthesis of Optically Enriched and Diazo Containing Tetrahydropyridazine.

A copper catalyzed enantioselective formal aza-Diels-Alder reaction of formed 1,2-diaza-1,3-dienes from α-halohydrazones and vinyl diazo compounds was described. The protocol provides a variety of optically enriched diazo-containing tetrahydropyridazines in moderate yields and with up to excellent enantioselectivities. The present methodologies utilize chiral oxazolines as the chiral ligands for asymmetric catalysis and feature mild reaction conditions, readily available substrates, and broad substrate scope.

Prevalence and characteristics of hereditary non-polyposis colorectal cancer (HNPCC) syndrome in immigrant Asian colorectal cancer patients.

Background: The prevalence of Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is 2 to 5% in the Caucasian population. HNPCC is caused by genomic mutations in DNA mismatch repair genes (MMR), namely MLH1, MSH2, MSH6, PMS2, and EPCAM. A non-hereditary, acquired process of hypermethylation of the MLH1 promoter can also lead to silencing of MLH1 protein expression.