Trauner

Trauner and coworkers released a report on a unified approach to isopropyl containing frans-hydrindane sesterterpenes via a common intermediate [38]. Their effort provided compounds that lend themselves to the substitution patterns embedded in retigeranic acids A (1) and B (2) as well as oxygenated precursors providing access to other sesterterpenes such as nitidasin (6), astellatol (3), and YW3699 (89). 

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Trauner and colleagues [39] recently found a striking contrast in the thermal and catalyzed reactions of a triene. Thermal reaction of a trienolate readily underwent disrotatory electrocyclization to afford cyclohexadiene (delocalization band in Scheme 8) in accordance with the Woodward-Hoffmann rule. Surprisingly, treatment of the trienolate with Lewis acid did not result in the formation of the cyclohexadiene but rather gave bicyclo[3.1.0]hexene in a [4n +2nJ manner (pseudoexcitation band in Scheme 8). The catalyzed reaction is similar to the photochemical reaction in the delocalization band. 

Trauner, D., Bats, J.W., Werner, A., Mulzer, J. (1998) Synthesis of EnantiomericaUy Pure Morphine Alkaloids The Hydrophenanthrene Route. Journal of Organic Chemistry, 63, 5908-5918. 

As mentioned previously, the Stille reaction can also be combined with an elec-trocyclization. Trauner and coworkers [99] used this approach for the synthesis of a part of SNF4435C (6/1-190) and its natural diastereomer. SNF4435C, which was isolated from the culture broth of an Okinawan strain of Streptomyces spectabilis, acts as an immunosuppressant and multidrug resistance reversal agent [100]. In order to form the annulated cyclobutane skeleton in 6/1-190, the vinyl iodide... 

We commenced our own approach toward ( )-phomactin A with an intent to feature an oxa-[3 + 3] annulation strategy [24—28] that was developed in our lab [29-32] and, in particular, an intramolecular annulation. While oxa-[3 + 3] annulations or related reaction manifolds [33, 34] are known and can be traced back more than six decades [35], an intramolecular variants of this reaction were not known [24—28]. There were no applications of intramolecular oxa-[3 + 3] annulations in natural product synthesis [27, 28, 36] until our approach toward phomactin A was disclosed. Subsequently, an account toward ( )-likonide B was reported by Trauner [36e],... 

For informative reviews on ring-closure in natural product synthesis, see (a) Beaudry CM, Malerich JP, Trauner D (2005) Chem Rev 105 4757 (b) Pindur U, Schneider GH (1994) Chem Soc Rev 409... 

Scheme 10.6 Trauner s synthesis of hydrindanone intermediates for sesterterpenes...

Scheme 10.7 Trauner s synthesis of ent-hydrindanone as intermediate for ent-retigeranic acid...

Trauner, M., Arrese, M., Lee, H., Boyer, J.L. and Karpen, S.J. (1998) Endotoxin downregulates rat hepatic ntcp gene expression via decreased activity of critical transcription factors. Journal of Clinical Investigation, 101, 2092-2100. 

The Trauner group utilized an olefin metathesis for the construction of the A-ring (Eq. 3) [131, 132] ... 

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