An Asymmetric Synthetic Approach to the A-ring of the Taxol Family of Anti-Cancer Compounds*
A synthetic route developed for the preparation of the A-ring of Taxol family of molecules is reported. By means of an intramolecular Diels-Alder reaction an asymmetric approach to this ring has been accomplished. Also, initial studies to prepare the A ring using an intramolecular Diels-Alder reaction have been successful.
Stereocontrolled synthesis of N,O-dimethyl-γ-amino-β-hydroxy acids : analogues of the (R)-MeIle-ψ(CHOMe)-Gly residue of the cytotoxic marine pseudopeptide dolastatin 10☆
Abstract The stereocontrolled synthesis of the N,O-dimethylated-γ-amino-β-hydroxy acid (R)-MeVal-ψ(CHOMe)-Gly ( 3b ) is reported; the key step is the formation of the nonmethylated allylic precursor with the anti configuration 20 by reduction of the keto analogue 16 .
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more