Nectandra rubra

The synthesis of the natural product rubrynolide from the Brazilian tree Nectandra rubra presents rather different problems. When the synthesis was planned it was supposed that rubrynolide was a trans lactone 135 but the third centre was not defined. The synthesis revealed that this structure is wrong the lactone is actually cis and the stereochemistry24 is 2S,4R,2 S 135a. 

Rubrenolide (39) (mp 100 °C, [aJo +21°) and rubrynolide (40) (mp 88 °C, [alo +21°) from Nectandra rubra (Lauraceae) are another type of y-lactones of alkene-alkyne pair (39). In these compounds, the alkene or alkyne substituent is attached to C-4 of the butanolide ring. 

Franca N C, Gottlieb O R, Coxon D T 1977 Rubrenolide and rubrynolide An alkene-alkyne pair from Nectandra rubra. Phytochemistry 16 257-262... 

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