Short and stereodivergent syntheses of (−)-5-epi-tashiromine and (−)-tashiromine and the formal synthesis of (−)-isoretronecanol and (−)-trachelanthamidine

A successful application of the Wittig-olefination–Claisen rearrangement protocol gave the allyl vinyl ether 12, which was efficiently converted into (−)-tashiromine alkaloids in a short sequence with high overall yield.

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tert-Butyl (S)-2-((S)-1-hydroxypent-4-en-2-yl)pyrrolidine-1-carboxylateC14H25NO3[α]D25 = −19.3 (c 1.0, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,S)

tert-Butyl (S)-2-((R)-1-hydroxypent-4-en-2-yl)pyrrolidine-1-carboxylateC14H25NO3[α]D25 = −26.7 (c 1.02, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,R)

tert-Butyl (S)-2-((S)-1-(benzyloxy)pent-4-en-2-yl)pyrrolidine-1-carboxylateC21H31NO3[α]D25 = −16.9 (c 1.4, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,S)

tert-Butyl (S)-2-((R)-1-(benzyloxy)pent-4-en-2-yl)pyrrolidine-1-carboxylateC21H31NO3[α]D25 = −23.2 (c 0.8, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,R)

tert-Butyl (S)-2-((S)-1-(benzyloxy)-5-hydroxypentan-2-yl)pyrrolidine-1-carboxylateC21H33NO4[α]D25 = −28.1 (c 1.1, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,S)

tert-Butyl (S)-2-((R)-1-(benzyloxy)-5-hydroxypentan-2-yl)pyrrolidine-1-carboxylateC21H33NO4[α]D25 = −34.6 (c 0.9, CHCl3)Source of chirality: (S)-prolineAbsolute configuration (S,R)

(8S,8aS)-8-((Benzyloxy)methyl)octahydroindolizineC16H23NO[α]D25 = −9.3 (c 1.6, MeOH)Source of chirality: (S)-prolineAbsolute configuration (S,S)

(8R,8aS)-8-((Benzyloxy)methyl)octahydroindolizineC16H23NO[α]D25 = −48.2 (c 0.8, MeOH)Source of chirality: (S)-prolineAbsolute configuration (S,R)

((8S,8aS)-Octahydroindolizin-8-yl)methanolC9H17NO[α]D25 = −1.9 (c 1.0, EtOH)Source of chirality: (S)-prolineAbsolute configuration (S,S)

((8R,8aS)-Octahydroindolizin-8-yl)methanolC9H17NO[α]D25 = −41.6 (c 0.9 EtOH)Source of chirality: (S)-prolineAbsolute configuration (S,R)