Prebiotic carbohydrate synthesis: zinc–proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
作者:Jacob Kofoed、Jean-Louis Reymond、Tamis Darbre
DOI:10.1039/b501512j
日期:——
Znâproline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose.
Mild and efficient method for the cleavage of benzylidene acetals by using erbium (iii) triflate
作者:Antonio Procopio、Renato Dalpozzo、Antonio De Nino、Loredana Maiuolo、Monica Nardi、Giovanni Romeo
DOI:10.1039/b511314h
日期:——
as new efficient Lewis acid catalyst in a mild deprotection protocol of benzylidene derivatives. In a modified procedure, where acetic anhydride is used as the reaction solvent, the simultaneous cleavage of the benzylideneacetal and the peracetylation of the substrates is obtained in quantitative yields and very short reaction times.
Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions
作者:Laurence Burroughs、Paul A. Clarke、Henrietta Forintos、James A. R. Gilks、Christopher J. Hayes、Matthew E. Vale、William Wade、Myriam Zbytniewski
DOI:10.1039/c1ob06798b
日期:——
Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under potentially prebiotic conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (L)-proline yield (L)-tetroses, esters of (L)-leucine, (L)-alanine and (L)-valine generate (D)-tetroses, offering the potential to account for the link between natural (L)-amino acids and natural (D)-sugars. The effect of pH and NaCl on the yields and enantioselectivities was also investigated and was shown to be significant, with the optimal enantioselectivities occurring at pH 7.
REGIOSELECTIVE BENZYLATION OF PENTITOLS, TETRITOLS, AND SOME HEXITOLS VIA THEIR STANNYL ETHER DERIVATIVES: VERSATILE SYNTHESIS OF MONOBENZYLALDITOLS
作者:Sami Halila、Mohammed Benazza、Gilles Demailly
DOI:10.1081/car-100106930
日期:2001.7.31
The xylitol, ribitol and D-arabinitol were transformed into their tributylstannyl ether derivatives by reaction with bis-tributyltin oxide [(nBU(3)Sn)(2)O I] and azeotropic removal of water. Subsequent benzyl etherification, using BnBr with solvent or under free solvent conditions, led regioselectively to primary mono-O-benzylalditol derivatives in satisfactory yields for a direct regioselective synthesis (similar to 52%). This etherification when applied to tetritols and some hexitols exhibits similar behaviour. With pentitols, an analogous study carried out with the n-dibutyltin oxide [nBU(2)SnO (II)] as the activating reagent showed contrasting results as regards regioselectivity.
Threitan and Erythritan and their Reaction with Periodate<sup>1</sup>