Total synthesis of antibiotic hygromycin A

Synthesis of aryl sialosides using Mitsunobu conditions

“…The Mitsunobu reaction 7 has been widely used for the synthesis of aryl glycosides, [8][9][10][11][12][13][14][15][16][17] acyl glycosides, [16][17][18][19] alkyl glycosides, 16,20,21 and amino glycosides 16,22 by reacting hemiacetals of aldosugars, predominantly glucose, galactose, and mannose, with weakly acidic acceptors in the presence of diethyl azodicarboxylate (DEAD) and triphenylphosphine (Ph 3 P). A major advantage of this direct dehydrative coupling procedure is that activated glycosyl donors do not need to be isolated and all reaction steps-anomerization, activation, and glycosidic bond formation-occur in a single series of events.…”

“…23 Due to the neutral conditions, the reaction is compatible with a wide variety of sensitive functionalities, ranging from epoxides and spiroketals to any of the commonly utilized protecting groups. 12,24 The stereochemical outcome depends on the anomeric ratio present in the hemiacetal and its mutarotation occurring under reaction conditions. Phenolic nucleophiles are good acceptors for this glycosylation reaction with aldosugars, leading to aryl glycosides.…”

Regioselective reductive openings of 4,6-benzylidene acetals: synthetic and mechanistic aspects

“…The acetal can be completely removed by for example mild acidic hydrolysis (usually 80% acetic acid in water), 13 iodine in methanol, 14,15 or by hydrogenolysis (Pd/C in acetic acid or Pd(OH) 2 in ethanol). 16,17 The benzylidene acetals can also be regioselectively opened under oxidative conditions, for example, by N-bromosuccinimide in CCl 4 under basic conditions (usually BaCO 3 ) to give a 4-O-benzoate and bromine in position 6.…”

Syntheses of Fumagillin and Ovalicin

“…[46] Commercially available 68, a derivative of d-glucose, was sensibly chosen as their starting material and was converted to 69 in four steps. [47] HgA C H T U N G T R E N N U N G (OTf) 2 -mediated, catalytic Ferrier rearrangement of enol ether 69 proceeded smoothly, and b elimination of the resulting alcohol 70 afforded enone 71 in 84 % yield over two steps. Reduction of 71 with NaBH 4 and CeCl 3 produced the corresponding alcohol as a single diastereomer, which was protected as its THP ether 72.…”