ABSTRACT
A novel approach to the synthesis of urea glycosides in aqueous media has been explored. Steyermark's glucopyranosyl oxazolidinone was found to be a good synthon for anchoring glucosyl moieties onto amines and thiols. The present method was successfully applied to establish a new route for the synthesis of urea-tethered neoglycoconjugates and pseudooligosaccharides in water.
Subject(s)
Glycoconjugates/chemical synthesis , Oligosaccharides/chemical synthesis , Urea/chemistry , Amines/chemistry , Carbohydrate Sequence , Glycosides/chemical synthesis , Glycosides/chemistry , Molecular Sequence Data , Oxazolidinones/chemistry , Sulfhydryl Compounds/chemistry , Urea/analogs & derivatives , Urea/chemical synthesis , Water/chemistryABSTRACT
A new method for the synthesis of urea-linked disaccharides in aqueous media has been developed. The key feature of our approach is two strained Steyermark-type gluco- and galactopyranosyl oxazolidinones. Each oxazolidinone is attached to a pyranose ring in a di-equatorial trans-annulation framework. Reaction of these oxazolidinones with 4-aminohexopyranose in water proceeded smoothly to afford the urea-tethered cellobiose and lactose analogues. The galactose-type oxazolidinone proved to be more reactive than the glucose-type, which is explained by the presence of an axial hydroxy group at C4 in the former.
Subject(s)
Cellobiose , Lactose , Urea/chemistry , Water/chemistry , Cellobiose/analogs & derivatives , Cellobiose/chemical synthesis , Cellobiose/chemistry , Glycosylation , Lactose/analogs & derivatives , Lactose/chemical synthesis , Lactose/chemistry , Molecular Structure , Oxazolidinones/chemistryABSTRACT
An efficient total synthesis of (+)-conagenin was achieved. The right fragment of conagenin, alpha-methylserine containing a quaternary stereocenter attached to nitrogen, was synthesized using allyl cyanate-to-isocyanate rearrangement. The left fragment, 2,4-dihydroxy-3-methylpentanoic acid, has three contiguous stereogenic centers, which was efficiently constructed by enantioselective monoreduction of 2-alkyl-1,3-diketones reported by Cossy, and chelation-controlled stereoselective reduction of beta-hydroxy ketone. These two fragments were coupled through intramolecular amide bond formation with high efficiency.
