Verzweigte und kettenverlängerte Zucker, XXX. Diastereoselektive Synthese von L‐glycero‐D‐manno‐Heptose, einem Baustein der inneren Core‐Region von Lipopolysacchariden

Large‐Scale Synthesis of Crystalline 1,2,3,4,6,7‐Hexa‐O‐acetyl‐L‐glycero‐α‐D‐manno‐heptopyranose

“…Because our ideal target was a crystalline and bench-stable storage form of 1 , solid peracetate 16a was selected, because it constitutes a versatile starting material for the preparation of thioglycosides, 12a heptosyl phosphates 22 or glycosyl donors such as imidates 23 or bromides. 24 The direct conversion of 1 into the corresponding pyranose peracetates 16a and 16b under either basic 5a , 25 or acidic 5b (H 2 SO 4 ) conditions has been reported, the latter giving almost pure α-pyranose form 16a on prolonged stirring in Ac 2 O/AcOH. However, in our experience this reaction is sluggish (days) at larger scale and its rate is highly dependent on the physical appearance of 1 (solid foam vs. syrup).…”

“…131.0–132.0 °C (EtOH) [lit: 127–129 °C (Et 2 O/hexane)] 29. [ α ] D 28 = +26 ( c = 1, CHCl 3 ) {ref 25. [ α ] D 24 = +27 ( c = 1, CHCl 3 )].…”

Are D-manno-configured Amadori products ligands of the bacterial lectin FimH?

“…Simple ozonolysis of the diastereomeric mixture 6 afforded a mixture of the protected D- glycero -D- galacto - and D- glycero -D- talo -configured heptoses 7a and 7b in quantitative yield. After sequential cleavage of the protecting groups, employing Zemplén conditions to remove acetyl groups [ 18 – 19 ] followed by acidic cleavage of the isopropylidene groups, the desired starting material for the Amadori rearrangement, a mixture of D- glycero -D- galacto /D- talo heptopyranoses ( 8a/b ) was obtained in an overall yield of 85% from 6 . This is a synthetic route to aldoheptoses 8a and 8b alternative to the one reported [ 2 ] with the advantage that the use of environmental hazardous as well as highly toxic HCN is not required.…”

β‐Selective C‐Glycosylation and its Application in the Synthesis of Scleropentaside A

“…[9] Furthermore, aCorey-Seebach reaction [10] of acarbohydrate to yield lactol 4,w hich had to be reduced subsequently,h as also been reported. [11] Recently Walczak et al reported across-coupling approach using glycosylstannanes 7 and super-stoichiometric amounts of copper salts. [12] Our approach employs ah eavy-metal-free umpolung reaction for the CÀCb ond formation at the anomeric centre.T he retrosynthetic analysis of scleropentaside A 1 indicates ad isconnection of the C À Cb ond and leads back to d-glucose (9)a nd furfural (10)a ss tarting materials (Scheme 3).…”