Carbohydrate synthons

Recent developments in the enzymatic synthesis of carbohydrates can be classified into four approaches 1) asymmetric C-C bond formation catalyzed by aldolases (1-10 2) enzymatic synthesis of carbohydrate synthons (loll) 3) asymmetric glycosidic formation catalyzed by glycosidases (12.-17) and glycosyl transferases (18-23.) and 4) regioselective transformations of sugars and derivatives (24-25). These enzymatic transformations are stereoselective and carried out under mild conditions with minimum protection of functional groups. They hold promise in preparative carbohydrate synthesis. In connection with this book, we focus on the first two approaches. 

Lundt I (2003) Iminosugars, isoiminosugars, and carbasugars from activated carbohydrate lactones efficient synthesis of biologically important compounds. In Witzak ZJ, Tatsuta K (eds) Carbohydrate synthons in natural products chemistry synthesis, functionalization and applications. ACS Symposium Series, vol 841. American Chemical Society, Washington, DC,pp 117-140... 

Gurjar, M. K. Ravindranadh, S. V. Karmakar, S. Mild and efficient methodology for installation of gem-diallyl functionality on carbohydrate synthons. Chem. Commun. 2001, 241— 242. 

Rigid Polycycles and Peptidomimetics from Carbohydrate Synthons... 

Carbohydrate synthons in natural product synthesis" which is the title of this special symposium has an inevitable problem to be solved, because we often need both enantiomers of synthons for the synthesis of optically active natural... 

Carbohydrate synthons in natural products chemistry synthesis, functionalization, and applications / Zbigniew J. Witczak, editor, Kuniaki Tatsuta, editor. 

Despite the greater awareness of carbohydrate synthons in recent years, the full potential of the carbohydrate chiral pool is still not... 

Witczak, Zbigniew J., Kuniaki Tatsuta, American Chemical Society Division of Carbohydrate Chemistry, and American Chemical Society. Carbohydrate Synthons in Natural Products Chemistry Synthesis, Functionalization, and Applications. ACS Symposium Series, no. 841. Washington, D.C. American Chemical Society, 2003. 

The rings of carbohydrate derivatives are excellent templates upon which a wealth of stereochemical features may be assembled, as was implied above in discussing the attributes of carbohydrate synthons. Having served its stereochemical purpose the sugar moiety may be destroyed so that it does not exist as a discrete entity in the product, although sections of it may survive. 

The formation of (153) rather than (151) indicated that the estabUsh-ment of correct stereochemistries at three centres (C-2, C-3, C-4) of the synthon (149) was not sufficient to ensure the stereochemistry at C-4 a of tetrodotoxin. Probably creation of the latter as a fourth chiral centre at C-5 of the carbohydrate synthon would be advantageous, and if the carbons attached to this centre were of vastly different acidities as in (157) the course of cyclisation would be controllable. 

---