Novel Stereoselective Reactgon of

Levoglucosenone (1), a readily availabie carbohydrate from the pyrolysis of cellulose, has been attracting attention as a chiral starting material with multifunctional groups.i) Its unique structure, being highly oxygenated but with no hydroxy greups, provides a great advantage for multi-step synthesis. Levog[ucosenone (1) requires none of the protect]'ere-deprotection steps of hydroxy groups that are required with other carbohydrates. The enone face is differ'entiated. by 1,6-allhydro-bridge and is useful for stereoseEective processes such as conjugate adciition, the Diels-Alder reaction, hydroxylation.i) We have aiready dernonstrated in our laboratory the usefulness of 1 as a chiron t-or the syntheses of complex natural products such as aUo-yohimban,2) reserpine,]} tautomycin,4) and tetrodotoxin,S) We describe here a novel highly stereoselective reaction between 1 and furfural (2), which was accidentally found during alarge-scale preparation of 1, Levoglucosenone was prepared in our laboratory by reported procedure.6) Pyrelysis of micro-crystals of cellulose (Aviceal@ from Asahi Kasei Co.) in the presence of an acid under reduced pressure gave a crude acidic distillate, this then being alkaiized and left to stand at rt without extraction. After several weeks, we surprisingly found that llevoglucosenone (1) had completely disappeared, and a new compound was apparent by TLC. NMR analyses gndicatecl that the new compound (3) was produced frem E and furfural (2), anothex major