Magnus synthesis

The sluggishness of the reaction of TIPSOTf with tertiary alcohols can be exploited to advantage, as was the case in Magnus synthesis of strychnine. The equilibrium favors the tertiary hemiketal, but silylation favors the primary alcohol. 

The Magnus synthesis of (+)-koumidine [(+)-3] (antipode of the naturally occurring alkaloid) (206) begins with the condensation of 111 with 2-... 

These relatively mild reducing agents can reduce the carbonyl of a lactone to give a lactol. In one example, 75 (an intermediate in Magnus synthesis of grandisol) was isolated in 97% yield when 74 was reduced with lithium triethoxyaluminum hydride at -20°C. It is known that trialkoxyaluminum hydrides will reduce aldehydes, ketones, esters and acid chlorides before reducing nitriles and amides. 

It is worth to mention here that compound 43 corresponded to prenirur-ine, a key intermediate in the Magnus synthesis of norsecurinine (27) and... 

Magnus prepared tetrahydrobenzofuran 37 using a Feist-Benary reaction of ethyl 2-chloroacetoacetate (32) and functionalized 1,3-cyclohexanedione 36. Compound 37 was a key synthetic intermediate in Magnus s synthesis of linderalactone, isolinderalactone, and niolinderalactone. ... 

N. S. Simpkins, Sulphones in Organic Synthesis [Tetrahedron Organic Chemistry], (J. E. Baldwin and R D. Magnus, eds.), Pergamon Press, Oxford, 1993. 

Scheme 21. The Barton reaction in Magnus s synthesis of grandisol (117).

In an approaeh to the synthesis of bisindole model systems developed by Magnus and co-workers, the inherent reactivity of precursor (35), activated by reaetion with phenylchloroformate, provides bisindole (37) as a mixture of diastereomers (67). In this reaction the indolenium intermediate (36) is probably the reacting species. 

Magnus, P. Mansl, T.E. (1999) Synthesis of the ABCD-rings ofthe insecticidal indole alkaloid nodulisporic acid. Tetrahedrcm Lett., 40,6909-12. 

R.M. Williams, Synthesis of Optically Active a-Amino-Acids- in J. E. Baldwin u. P. D. Magnus, Organic Chemistry Series Vol. 7, S. 270, Pergamon Press, Oxford New York Beijing Frankfurt Sao Paulo Tokyo - Toronto 1989. 

Magnus and co-workers7 have used a related desilylation for a novel synthesis of I la-hydroxyestrone methyl ether (8) from the epoxide (7) via an o-xylylene intermediate,... 

---