Effective synthesis of novel C(2)-propargyl derivatives of betulinic and ursolic acids and their conjugation with β-d-glucopyranoside azides via click chemistry

Effective Synthesis of a Novel Tetrahydrofuran Containing Triterpenoid: 5′(Z)-Benzylidene-tetrahydrofurano[3,2-b]lup-20(29)-en-28-oate

“…Silica gel L (KSKG grade, 50-160 μm) was employed for column chromatography. Starting triterpenoid 4 was prepared as previously reported [15]. NMR spectra of all new compounds are in Supplementary Materials.…”

“…Recently, we developed an efficient method for the synthesis of 2-propargyl 3-oxo-triterpene acid derivatives [14]. The resulting triterpene compounds containing a 4-pentyn-1-one structural unit in ring A have been successfully used in the anionic 5-exo-dig cycloisomerization induced by a strong base, KN(SiMe 3 ) 2 -DME [15]. The heterocyclization of these compounds also was performed in the presence of Au(I) + phosphine complexes [16].…”

Effective synthesis of novel furan-fused pentacyclic triterpenoids via anionic 5-exo dig cyclization of 2-alkynyl-3-oxotriterpene acids

“…28 A 1 M solution of KN(SiMe3)2 (0.51 mL, 0.51 mmol) in THF was added to a solution of triterpenoids 8-10 (0.39 mmol) in DME (6 mL). The reaction mixture was stirred at room temperature under an argon atmosphere.…”

“…28 In this work, the С-2 alkynyl derivatives of 3-oxotriterpene acids were used as the key intermediates for the synthesis of new furanоtriterpenoids by anionic 5-exo-dig cyclization of the pent-4-yn-1-one moiety in the A-ring of the pentacyclic skeleton. A specific feature of this transformation is that the pent-4-yn-1-one moiety is incorporated in polycyclic molecules, structurally related to steroids, whereas in many cases, acyclic alkynyl ketones have been used as the initial substrates for cyclization into furans.…”

“…Under the optimized conditions, methyl ursonate 9 and methyl oleonate 10 were converted to heterocyclic compounds 12a and 13a in 56% and 54% yields, respectively (Scheme 2, Table 1). Demethylation of the sterically hindered ester group in compounds 11a-13a via halideolysis with LiI in DMF 28 afforded 11b-13b in 54-56% yield (Scheme 2). In order to broaden the applicability of this method, aryl groups with various substituents in the aromatic ring (4-Cl, 4-Br, 4-F, 3,4,5-(OMe)3, 2-Me, 4-NO2) were introduced into the terminal acetylenic moiety of compounds 8-10.…”