Access to Diosgenyl Glycoconjugates via Gold(I)-Catalyzed Etherification of Diosgen-3-yl ortho-Hexynylbenzoate

Abstract

An efficient protocol for the synthesis of diverse diosgen-3-yl glycoconjugates, a class of novel synthetic analogs of natural saponins of biological significance, has been developed. The method relies on gold(I)-catalyzed etherification of diosgen-3-yl ortho-hexynylbenzoate with stoichiometric sugar alcohols to afford the corresponding glycoconjugates in 38%-99% yields. The reaction involves the preferential attack of hydroxyl groups to the C3 position of homoallylic carbocation intermediate and displays a broad substrate scope and a good functional group tolerance.

The Catalytically Lignan-Activation-Based Approach for the Synthesis of (epi)-Podophyllotoxin Derivatives

“…Capitalizing on the appealing low oxophilicity and the excellent functional-group-compatible properties of the gold catalyst, ortho -alkynyl benzoate has been widely applied in organic synthesis . Inspired by these precedented works, we assume that (E)-PPT 4- O - ortho -cyclopropylethynylbenzoates can act as ideal intermediates for a highly efficient derivatization of (E)-PPTs.…”

“…Conventional (E)-PPT derivatization methods suffer from moderate-to-low efficiencies and harsh reaction conditions . Recently, the first catalytic glycosylation derivatization of (E)-PPTs was developed by us on the basis of the Yu glycosylation . Nevertheless, this method can only afford anomerically linked (E)-PPT-4- O -glycosides .…”

β-Glycosylations with 2-Deoxy-2-(2,4-dinitrobenzenesulfonyl)-amino-glucosyl/galactosyl Selenoglycosides: Assembly of Partially N-Acetylated β-(1 → 6)-Oligoglucosaminosides

“…Following general procedure A, 3 (59.0 mg, 72.0 μmol, 1.0 equiv) was treated with PhSeCl (13.8 mg, 72.0 μmol, 1.2 equiv) and AgOTf (37.0 mg, 144.0 μmol, 2.4 equiv), followed by addition of 4m (33.0 mg, 60.0 μmol, 1.0 equiv) in DCM/CH 3 CN (3.1 mL, v/v = 2.6/0.5), to give 5m (62.5 mg, 51.6 μmol, 86%) as a white foam after purification by silica gel column chromatography (petroleum ether/dichloromethane/ethyl acetate = 4:1:1). 1 H NMR (400 MHz, chloroform- d ): δ 8.48 (d, J = 2.2 Hz, 1H), 8.11 (dd, J = 8.6, 2.2 Hz, 1H), 7.99 (d, J = 8.6 Hz, 1H), 7.47–7.27 (m, 21H), 7.22–7.17 (m, 4H), 6.83–6.77 (m, 4H), 6.17 (d, J = 9.0 Hz, 1H), 5.02 (d, J = 10.3 Hz, 1H), 4.90–4.82 (m, 2H), 4.76 (d, J = 10.3 Hz, 1H), 4.58–4.50 (m, 6H), 4.49–4.43 (m, 3H), 4.39 (d, J = 2.4 Hz, 1H), 3.79 (s, 3H), 3.68–3.50 (m, 5H), 3.44 (dd, J = 10.1, 3.1 Hz, 1H), 3.41–3.35 (m, 1H), 3.29 (m, 3H), 1.15 (s, 9H).…”

Cycloisomerization of π‐Coupled Heteroatom Nucleophiles by Gold Catalysis: En Route to Regiochemically Defined Heterocycles

“…As rationalized by the authors, the reaction starts with Au(I)‐mediated 6‐ endo ‐ dig selective cyclization 109 a trailed by nucleophilic attack on 109 b . On an application side, this sort of chemistry is immensely used in the alkylation of sugar derivatives and valuable fine‐chemicals [213–232] …”