Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

Abstract

Compounds containing two alkyne groups in close vicinity at the rigid skeleton of camphorsulfonamide show unique reactivities when treated with electrophiles or catalytic amounts of platinum(II). The formed product structures depend not only on the reagents used but also on the substituents attached to the triple bonds. Cycloisomerisations with perfect atom economy lead to polycyclic heterocycles that resemble to some extent the AB ring system of paclitaxel. Herein, we present practical synthetic methods for the selective synthesis of precursor dialkynes bearing different substituents (alkyl, aryl) at the triple bonds, based on ketals or an imine as protecting groups. We show for isomeric dialkynes that the reaction cascade induced by Pt(II) includes ring annulation, sulphur reduction, and ring enlargement. One isomeric dialkyne additionally allows for the isolation of a pentacyclic compound lacking the ring enlargement step, which we have proposed as a potential intermediate in the catalytic cycle.

Cyclic Sulfinamides

“…The proposed mechanism implies the formation of intermediate 205 (Scheme 83). [129][130][131] Sulfonamide reduction under oxidizing conditions in the above camphorsultam derivative 204 b looks even more puzzling! Thus, the reaction with Br 2 initialized another cascade reaction eventually affording the mixture of bisbrominated polycyclic sultims 208 and 209.…”

Synthesis and Structural Determination of 6-O-prop-2-ynyl-1,2:3,4-di-O-Isopropylidene-α-D-Galactose

“…1) that found in the tallowwood tree or Eucalyptus microcorys. Various alkynes possess remarkable biological activity and they have been utilised as drugs, 7,8 for example, the birth control medicine norethynodrel. 9 In addition, it was reported that some of the natural acetylenes i.e.…”