Glucal

About: Glucal is a research topic. Over the lifetime, 590 publications have been published within this topic receiving 8960 citations. The topic is also known as: D-glucal.

Stereocontrolled total synthesis of polygalolide A.

Abstract: The total synthesis of polygalolide A, a secondary metabolite that was isolated from a Chinese medicinal plant, is reported. A key issue in this synthesis was construction of an oxabicyclo[3.2.1] skeleton, which was solved by the development of an intramolecular Ferrier-type C-glycosylation of a glucal with siloxyfuran as an internal nucleophile. The substrate was prepared from D-glucal by the introduction of trimethylsilylacetylene and siloxyfuran groups. Although C-glycosylation did not occur under the conditions found from model experiments, further examination revealed that the combination of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,4,6-collidine successfully afforded the desired product as a single diastereomer. The siloxy group at the C3 position played a crucial role in the stereocontrol of this reaction. The product was further transformed into a tetracyclic compound as follows: The vinyl ether and acetylenic moieties were reduced and the siloxy group was removed with a Barton–McCombie reaction. The construction of the six-membered ether and the γ-lactone provided the tetracyclic compound. Finally, a phenolic moiety was introduced by using a Mukaiyama aldol reaction to furnish polygalolide A.

Copper(II) Triflate as a Mild and Efficient Catalyst for Ferrier Glycosylation: Synthesis of 2,3-Unsaturated O-Glycosides

Abstract: Various acceptors including carbohydrates, amino acids, natural products, and hydroxylamine derivatives were coupled with 3,4,6-tri-O-acetyl- d -glucal in the presence of Cu(OTf)2 as catalyst. The protocol offers facile and efficient Ferrier glycosylation for the synthesis of 2,3-unsaturaed O-glycosides in good yields and high anomeric selectivity.