Selective allylation of sugar derivatives containing the 1,1,3,3‐tetraisopropyldisiloxane‐1,3‐diyl protective group

Abstract

Abstract. Using the method of Guibe et al. we were able to selectively introduce an allyl group at the 2-position in methyl-4,6-O-(tetraisopropyldisiloxane-l,3-diyl)-a-~-glucopyranoside and benzyl--4,6-O-(tetra~sopropyldisiloxane-1,3-d~yl)-~-~-glucopyranoside. The dynamic properties of the tetraisopropyldisiloxane-l,3-diyl protective group gave us access to a glucose derivative which carried a I-propenyl group at the 2-position, an allyl group at the 6-position and a tetraisopropyldisiloxane-l,3-diyl at the 3,4-position together with a glucose derivative protected with an allyl, an acetyl and a 3-hydroxytetraisopropyldisiloxanyl at the 2-, 3-and 4-positions, respectively.

Total Synthesis and Structural Elucidation of the Antifungal Agent Papulacandin D

“…Attempts to convert the crude tetraol 14 into the corresponding acetals with anisaldehyde, 2,4-dimethoxybenzaldehyde, or 4-methoxyacetophenone also proceeded in variable yet low yields. Saponification of the tetraacetate 17 gave the crude tetraol 14 which was directly condensed with 1,1,3,3-tetraisopropyl-1,3-dichlorodisiloxane. , 1 H NMR spectroscopy of the crude reaction mixture was consistent with partial de- tert -butylsilylation, and chromatography gave a spiroketal tentatively assigned as the adduct 22 in only modest yield (50%). It is clear from these results that the Zemplen methanolysis step was the source of the trouble rather than acid-mediated de- tert -butylsilylation during acetal formation.…”

Allylation of Erythromycin Derivatives: Introduction of Allyl Substituents into Highly Hindered Alcohols

“…While Sinou's group has reported moderate to excellent yields in the allylation of carbohydrate substrates using allyl ethyl carbonate, an excess (2−6 equiv) of the allylating agent was required . It seemed likely that the spectator alkoxy group liberated from the carbonate competes with the desired nucleophile for the π-allyl palladium reagent.…”

High yielding allylation of a chiral secondary alcohol containing base sensitive functional groups

“…In general, this hypothesis is attributed to Sinou and coworkers, who used allyl ethyl carbonate with Pd 0 to form the allyl ether of carbohydrate substrates, 6 but there are also other variations. In one example, an allyl carbonate precursor was formed from the alcohol substrate, 7 which was then treated with the palladium catalyst. Under strictly anhydrous conditions, this implies only one nucleophile (the alkoxide of the substrate) would be present to trap the allylcation, and the rate limiting step in the reaction would be the attack of the π-allyl complex by the alkoxide, since the acid-base equilibrium shown in step 2 of Scheme 2 would not be present in the mechanism.…”