Semisynthesis of New D-seco-C-nor-Taxane Derivatives Containing a Polyfunctionalized Furanosyl or Cyclopentenyl or Cyclopentyl C-Ring

Abstract

The synthesis of new D-seco-C-nor-taxane derivatives in which the D-ring has been deleted and the C-ring has been transformed into a new pentatomic ring, i.e., the polyfunctionalized tetrahydrofuranosyl and cyclopentenyl or cyclopentyl ring, was performed starting from baccatin III derivatives. The synthetic strategy adopted took advantage of the oxetane ring opening and disconnection of the C4-C5 bond, followed by an intramolecular condensation. The formation of furanosyl or cyclopentyl rings is strictly dependent on the presence of unprotected or protected oxygen at C-7 in the starting material. The reactions proceeded with good diastereoselectivity with control of the stereochemistry of one or two stereocenters.

Mechanically activated ring-opening reactions of N-acyl-1,2,3,4-tetrahydroisoquinolines derived from the synthesis of praziquantel intermediate

“…The oxidative ring opening of heterocycles, 6 metal-containing heterocycles 7 and carbocycles 8 are well documented, these valuable ring-opened synthetic intermediates can be further manipulated to afford ring-contraction or ring-expansion products. 9 In addition, a great number of works have applied oxidative ring opening reaction to the synthesis and modification of bioactive natural products, such as Lavandulol, 10 (þ)-Lycoricidine, 11 Taxane derivatives 12 and Paclitaxel analogs. 13 However, most of the oxidative ring-opening reactions are conducted in hazardous organic solvents, together with metal oxidants or other explosive oxidants.…”

Aphadilactones A–D, Four Diterpenoid Dimers with DGAT Inhibitory and Antimalarial Activities from a Meliaceae Plant

“…Fortunately, after dihydroxylation with potassium osmate, compound 1 gave the three products 10a – 12a in isolated yields of 13–15%, as expected. Each of these was further oxidized with Pb(OAc) 4 and then reduced with NaBH 4 , and the resulting reaction mixtures were directly subjected to chiral HPLC analysis. One HPLC peak at ca.…”

“…Compound 10a (1.0 mg) was dissolved in dried CH 2 Cl 2 (1 mL), and a fresh batch of lead tetraacetate (1.0 mg) was slowly added at 0 °C . After the raw material was completely converted (as monitored by TLC), an excess of newly prepared methanolic solution of NaBH 4 was added, and the reaction was continued for 10 min .…”

“…Compound 10a (1.0 mg) was dissolved in dried CH 2 Cl 2 (1 mL), and a fresh batch of lead tetraacetate (1.0 mg) was slowly added at 0 °C. 20 After the raw material was completely converted (as monitored by TLC), an excess of newly prepared methanolic solution of NaBH 4 was added, and the reaction was continued for 10 min. 21 After workup, the resulting product was subsequently subjected to chiral HPLC analysis (chiral AD-H column, 10 mm × 250 mm, Daicel Chemical Industries, Ltd.) with n-hexane/isopropanol (2.7:0.3) as the mobile phase.…”

Antimalarial diterpenoid dimers of a new carbon skeleton from Aphanamixis grandifolia

“…The residue (a mixture of i and ii, Scheme S1, ESI †) was then dissolved in dried DCM (1.0 mL), and a fresh batch of Pb(OAc) 4 (1.0 mg) was slowly added at 0 °C (ref. 15) until the raw material was completely converted (monitored by TLC). After the work-up, the resulting product was purified by semi-preparative HPLC (CH 3 CN-H 2 O, 6 : 4) to afford compounds 4a (0.4 mg) and 4b (1.0 mg).…”