Stereoselective total synthesis of (+)-synargentolide A

The stereoselective synthesis of synargentolide A, a polyhydroxy δ-lactone, has been accomplished from tartaric acid. The key steps in the synthesis involve Keck and Brown allylations and ring closing metathesis.

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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)

(4R,5R)-4-((R)-1-(Methoxymethoxy)but-3-enyl)-2,2,5-trimethyl-1,3-dioxolaneC12H22O4[α]D = +76.5 (c 1.3, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (4R,5R)

(R,E)-Ethyl 5-(methoxymethoxy)-5-((4R,5R)-2,2,5-trimethyl-1,3-dioxolan-4-yl)pent-2-enoateC15H26O6[α]D = +54.7 (c 1.9, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,4R,5R)

(R,E)-5-(Methoxymethoxy)-5-((4R,5R)-2,2,5-trimethyl-1,3-dioxolan-4-yl)pent-2-en-1-olC13H24O5[α]D = +57.9 (c 1.5, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,4R,5R)

(E,4R,8R)-8-(Methoxymethoxy)-8-((4R,5R)-2,2,5-trimethyl-1,3-dioxolan-4-yl)octa-1,5-dien-4-olC16H28O5[α]D = +49.3 (c 2.8, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,4R,8R,5R)

(R)-6-((R,E)-4-(Methoxymethoxy)-4-((4R,5R)-2,2,5-trimethyl-1,3-dioxolan-4-yl)but-1-en-1-yl)-5,6-dihydro-2H-pyran-2-oneC17H26O6[α]D = +83.4 (c 1.0, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,4R,5R)

(E,2R,3R,4R)-7-((R)-6-Oxo-3,6-dihydro-2H-pyran-2-yl)hept-6-ene-2,3,4-triyl triacetateC18H24O8[α]D = +66.4 (c 1.0, CHCl3)Source of chirality: l-(+)-tartaric acidAbsolute configuration: (E,2R,3R,4R)