Die Synthese des Labdanditerpenes Erigerol und analoger Verbindungen

Abstract

The Synthesis of the Labdane Diterpenoid Erigerol and of Analogous CompoundsThe synthesis of Erigerol (1) and of analogous compounds in a 23-step sequence is described. The various difficulties of the synthesis and several blind alleys that have been followed are discussed.Einleitung. -Erigerol (l), ein Vertreter der Labdanditerpene, wurde neben vielen

A Concise Synthesis of Forskolin

“…In our synthetic planning, we considered cis-decalin 3 (Scheme 1) as an early intermediate,because its ring systems map onto the decalin substructure of forskolin (1)a nd it is readily prepared on amultigram scale using aflexible Diels-Alder strategy developed by researchers at Hoffmann-La Roche (8 steps from the commercially available materials). [9] Although decalin intermediates of this type were contemplated already some 30 years ago, [10] their conversion into forskolin (1)eluded efficient synthetic solution. As astrategic objective,wetherefore targeted concise construction of the gpyrone ring of forskolin (1)from cis-decalin 3.Anisoxazolebased route described below emerged as attractive due to the minimum of redox and protecting group manipulations required by such an approach.…”

Enantioselective Synthesis of the Hydroazulene Core of 3α‐Hydroxy‐15‐rippertene

“…Hydroboration of 7 follows the stereochemical course already observed with 6 [10] through minimization of allylic strain. [11] After copper-induced allylic substitution with methallyl bromide and deprotection of the intermediate silyl ether with aqueous HCl, [12] the enantiomerically pure alcohol 8 was isolated in excellent yield with Ͼ98 % de (GC). PCC oxidation [13] of 8 to give the ketone 9 and a Lewis acid catalyzed ring expansion of 9 with (trimethylsilyl)diazomethane [14] afforded the cycloheptanone 10 after hydrolysis of the trimethylsilyl enol ether intermediate.…”

Untersuchungen zur Stabilität und Reaktivität von (3‐Cyclopropylidenprop‐1‐enyl)‐ethyl‐ether

“…Diese Addukte konnen als sehr geeignete Synthese-Bausteine fur Diterpene vom Labdan-Typ wie z. B. Erigerol dienen [2] [3]. l a R = E t lb R=MeCO Dien l b hingegen reagiert mit 2,6-Dimethylchinon nur unter verscharften Bedingungen (1 SO0) und in unbefriedigender Ausbeute (38 YO) [4] Im Vergleich zu l a gab l b unter den oben angefuhrten Reaktionsbedingungen keine nachweisbaren Dimere.…”

“…Allgemeines. Herstellung von l a [l] und l b [4]; DC, Schmp., spektroskopische Methoden, s. [3]. Korrekte Elementaranalysen innerhalb der ublichen Fehlergrenzen wurden von allen kristallinen Verbindungen erhalten und werden nicht speziell erwahnt.…”