142865-94-9Relevant academic research and scientific papers
Total synthesis of the postulated structure of fulicineroside
Bartholom?us, Ruben,Dommershausen, Fabian,Thiele, Markus,Karanjule, Narayan S.,Harms, Klaus,Koert, Ulrich
supporting information, p. 7423 - 7436 (2013/06/27)
A total synthesis of the proposed structures of fulicineroside and its aglycone fulicinerine is reported. The tetrasubstituted dibenzofuran substructure was accessible either through a Pd-mediated ortho-metalation or by an Ir-catalyzed meta-borylation. The synthesis of the β,β,α- linked trisaccharide consisting of D-olivose, L-rhodinose, and L-rhamnose was challenged by the unprecedented β-linked rhodinose. A Pd-catalyzed β-selective glycosylation of a 4-epi-rhodinose and a subsequent Mitsunobu inversion provided selectively the β-linked L-rhodinose-L-rhamnose disaccharide. Comparison with the reported data for the natural product and the aglycone suggests a misassignment of the structure of the natural product. Natural product reassignment: Total synthesis of the proposed structures for fulicineroside and its aglycone fulicinerine has been achieved (see figure). Key issues were the tetrasubstituted dibenzofuran and the trisaccharide with its β-linkage between L-rhodinose and L-rhamnose. A comparison with the reported data for the natural product and the aglycone suggests a misassignment of the structure of the natural product. Copyright
Stereoselective synthesis of 2-deoxy-β-glycosides from glycal precursors. 2. Stereochemistry of glycosidation reactions of 2-thiophenyl- and 2-selenophenyl-α-D-gluco-pyranosyl donors
Roush, William R.,Sebesta, David P.,James, Ray A.
, p. 8837 - 8852 (2007/10/03)
We have demonstrated that 4-O-acetyl-6-bromo-3-O-(tert- butyldimethylsilyl)-2-deoxy-2-thiophenyl-1-trichloroacetimido-α-D- glucopyranose 11b is the most efficient and selective donor for use in the synthesis of 2-deoxy-β-glycosides of the series of glycosyl donors examined. Unlike the 2-selenophenyl substituted donors 8 which proved to be configurationally unstable under standard TMS-OTf promoted glycosylation conditions, giving rise to α-manno glycosides 14, 17 and 20 from β-gluco donors 8, the 2-thiophenyl substituted donors 9 and 11 appeared to be completely configurationally stable (at C(2)). The main problem with imidates 11 is that the stereoselectivity of their reactions with alcohols is substrate dependent, with best selectivity for the desired β-glycosides 35 and 42 being obtained with the least sterically hindered alcohols. The fact that the α-glycosides 36 and 43 comprise up to 20-50% of the product in glycosidation reactions of hindered secondary alcohols supports the thesis that the reaction stereoselectivity is not governed by the intermediacy of episulfonium ions (47 and 47'), but rather that substitution reactions of oxonium ions 46 and its conformationally inverted isomer 46' play a dominant role.
Synthesis of C-D-E Trisaccharide Precursors of Olivomycin A
Sebesta, David P.,Roush, William R.
, p. 4799 - 4802 (2007/10/02)
Syntheses of functionalized C-D-E trisaccharide precursors (16, 5) of olivomycin A are reported.A stereoselective C-D β-glycosidation was accomplished by employing 2-deoxy-2-(phenylthio)-α-glucotrichloroacetimidate 8.The α-D-E glycosidic linkage was intro
