Total synthesis of (−)-ent-pachastrissamine (ent-Jaspine B)

The total synthesis of the enantiomer of the tetrahydrofuran containing natural product Jaspine B is reported. The key reactions in the synthesis include formation of the tetrahydrofuran unit by an acid mediated Williamson etherification and a subsequent elaboration with an olefin cross metathesis reaction.

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(1S,2R)-1-(Benzyloxy)-1-((S)-2,2-dimethyl-1,3-dioxolan-4-yl)pent-4-en-2-olC17H24O4[α]D = −29.0 (c 2.1, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (1S,2R)

(2S,3R,4R)-3-(Benzyloxy)-4-(methoxymethoxy)hept-6-ene-1,2-diolC16H24O5[α]D = −46.2 (c 0.8, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (2S,3R,4R)

(2S,3S,4R)-3-(Benzyloxy)-4-(methoxymethoxy)hept-6-ene-1,2-diyl methylbenzenesulfonateC30H36O9S2[α]D = −15.2 (c 3.8, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (2S,3S,4R)

(3S,4S,5R)-5-Allyl-4-(benzyloxy)tetrahydrofuran-3-yl 4-methylbenzenesulfonateC21H24O5S[α]D = −44.7 (c 1.1, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (3S,4S,5R)

(3R,4R,5R)-5-Allyl-N-benzyl-4-(benzyloxy)tetrahydrofuran-3-amineC21H25NO2[α]D = +51.0 (c 1.9, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (3R,4R,5R)

(3R,4R,5R)-N-Benzyl-4-(benzyloxy)-5-((E)-tetradec-2-en-1-yl)tetrahydrofuran-3-amineC32H47NO2[α]D = +25.6 (c 0.4, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,3R,4R,5R)

TFA salt of ent-Jaspine BC20H38F3NO4[α]D = −16.4 (c 0.4, EtOH)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (3R,4R,5R)

(2R,3R,4R)-4-Amino-2-tetradecyltetrahydrofuran-3-ol [ent-pachastrissamine (ent-Jaspine B)]C18H37NO2[α]D = −17.7 (c 0.4, EtOH)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (2R,3R,4R)