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.
Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
作者:Laurence Burroughs、Matthew E. Vale、James A. R. Gilks、Henrietta Forintos、Christopher J. Hayes、Paul A. Clarke
DOI:10.1039/c0cc00613k
日期:——
Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose underaqueousconditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (L)-proline yield (L)-carbohydrates, esters of (L)-leucine and (L)-alanine generate (D)-carbohydrates, offering the potential to account for the prebiotic link between natural (L)-amino acids
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.
Abstract Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4. Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups. Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are