Organotransition metal modified sugars: Part 21. Synthesis of organometallic disaccharides bearing two monosaccharide moieties linked by a chromium carbene spacer

Abstract Organometallic disaccharides containing a chromium carbene spacer have been synthesized from tetramethylammonium acetyl(pentacarbonyl)chromate(-I) ( 1 ) in a two-step protocol. An acylation/alcoholysis sequence applying di(isopropylidene)-protected glucose, mannose, galactose and fructose afforded O -glycoside methylcarbene complexes 6 – 9 in 29–84% yield. Upon reaction with 1,2:3,4-di- O -isopropylidene-α- d -galacto-hexodiald-1,5-ose, activated by TiCl 4 , they undergo a trans -selective aldol condensation to give a 53–89% yield of chromium vinylcarbene O , C -disaccharides ( 10 – 13 ) which are promising candidates for subsequent benzannulation, cyclopropanation, Diels–Alder- and Michael addition reactions.