Boc-N-methyl-L-valine → (3aR,4S,7aR)-4-[(S)-2-(tert-butoxycarbonyl-methyl-amino)-3-methyl-butyryloxy]-4-m-tolylethynyl-octahydro-indole-1-carboxylic acid methyl ester

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Reaction Steps

Synthesis in analogy to the General Method 1 starting from (3aS,4R,7aS)-4-hydroxy-4-m-tolylethynyl-octahydro-indole-1-carboxylic acid methyl ester and (S)-2-(tert-butoxycarbonyl-methyl-amino)-3-methyl-butyric acid to yield (3aR,4S,7aR)-4-[(S)-2-(tert-butoxycarbonyl-methyl-amino)-3-methyl-butyryloxy]-4-m-tolylethynyl-octahydro-indole-1-carboxylic acid methyl ester. This NBoc-protected product was then stirred in hydrochloric acid dioxane solution (4M, 10 equiv.) at room temperature for 6 hrs. Subsequently the solvent was removed the residue dissolved in dichloromethane and washed with saturated sodium hydrogencarbonate solution. The organic layer was tried with sodium sulfate, filtrated and evaporated. The crude product was subjected to silica gel flash chromatography (ISCO CombiFlash; dichloromethane/methanol; 100/0 to 95/5) to yield (3aR,4S,7aR)-4-((S)-3-methyl-2-methylamino-butyryloxy)-4-m-tolylethynyl-octahydro-indole-1-carboxylic acid methyl ester. MS [M+H]=296 (ester elimination ion); RT=5.490 min; HPLC Method I

Provenance & Evidence