2‐Methyltricyclo[3.2.1.0^2,7]octan‐6‐ol, ein Modell für die Fragmentierung von Helifulvanolsäure

Abstract

2-Methyltricyclo[3.2.1 .02~710clan-6-ol, a Model for the Fragmentation of Helifulvanolic AcidThe epimeric 2-methyltricyclo[3.2.1 .d*']octan-6-ols 7 and 8, models for the fragmentation of helifulvanolic acid, have been synthesized starting from 4-methyl-3-cyclohexenecarboxylic acid.While an oxidative fragmentation of 7 and 8 could not be observed, a very similar fragmentation of both tosylates 9 and 10 occurred.Bei der Strukturaufklarung einer Diterpensaure aus einer Helichrysum-Art hatten wir versucht, den Helifulvanolsaure-methylester (1) mit Pyridinium-chlorochromat in das entsprechende Keton zu iiberfuhren I). Uberraschenderweise isolierte man jedoch auschliefllich das Dien 3. Wahrscheinlich entsteht 3 durch Fragmentierung des primar gebildeten Chromsaureesters 2. Urn die Voraussetzungen fur eine derartige, unseres Wissens noch nicht beobachtete Reaktion zu untersu-

Carbon atom insertion bicycloannulation: total syntheses of ishwarane and ishwarone

“…22), had already proven the utility of the CAIB methodology. Although the octalin, 62 (Scheme 7), required for a CAIB synthesis of ishwarane (1) could conceivably have been prepared from octalone 5 by Wolff-Kishner reduction, the length of the sequence leading to 5 as well as the loss of considerable material at the epoxide cyclization stage dictated a search for more efficient possibilities for the synthesis of the ~ctalin.~'…”

“…To a mixture of 4.0 g (32 mmol) of bromoform, 2.0 g (16 mmol) of 1,5,5-trimethylcyclohexene (22) (47) (containing 15% of the isomer, 1,3,3-trimethylcyclohexene, 26), and 0.032 g of benzyltriethylammonium chloride was added dropwise, with stirring, 8 mL of 50% aqueous sodium hydroxide over 10 min, keeping the temperature in the range 40-45°C by means of a cold water bath. Stirring was continued at this temperature for 3 h, and the mixture was then poured into 250 mL of water.…”

“…I 1, 14, and 17. An attempted, but unsuccessful, synthesis of ishwarone has also been reported (18). h his ring system is also present in another sesquiterpene, cycloseychellene (20), and in the trachylobane (21) and helifulvane (22) series of diterpenoids. For an alternative approach to the rapid construction of this system, see our synthesis of trachyloban-19-oic acid (23) and ref.…”