A concise approach to both enantiomers of phytoprostane B1 type II

The synthesis of enantiomeric phytoprostane B1 type II methyl esters has been accomplished in approximately 30% overall yield via two basic transformations starting from 3-[(dimethoxyphosphoryl)methyl]cyclopentenone as a key reagent. They include ethylation of the ring C(2) carbon and a Horner olefination reaction using the phosphonate moiety at C(3). The novel components of the Horner reaction, the enantiomeric methyl 9-formyl-9-hydroxynanoates, were easily prepared from racemic methyl 9-hydroxy-10-undecenoate via asymmetric Sharpless epoxidation (kinetic resolution) followed by ozonolysis.

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(S)-Methyl 9-hydroxy-10-undecenoateC12H22O3ee >98%[α]D20=+5.75 (c 1.2, CHCl3)Source of chirality: diisopropyl d-tartrateAbsolute configuration: (S)

(S)-Methyl 9-(tert-butyldimethylsilyloxy)-10-undecenoateC18H36O3ee >98%[α]D20=+6.1 (c 2.97, CHCl3)Source of chirality: diisopropyl d-tartrateAbsolute configuration: (S)

(S)-Methyl 9-(tert-butyldimethylsilyloxy)-9-formyl-nonanoateC17H34O4Siee >98%[α]D20=-20.6 (c 2.57, CH2Cl2)Source of chirality: diisopropyl d-tartrateAbsolute configuration: (S)

10E-(S)-Methyl 11-(2-ethyl-3-oxo-cyclopent-1-enyl)-9-(tert-butyldimethylsilyloxy)-undec-10-enoateC25H44O4Siee >98%[α]D20=-2.1 (c 1.86, CH2Cl2)Source of chirality: diisopropyl d-tartrateAbsolute configuration: (S)

10E-(S)-Methyl 11-(2-ethyl-3-oxo-cyclopent-1-enyl)-9-hydroxyundec-10-enoateC19H29O4ee >98%[α]D20=-24.1 (c 2.07, MeOH)Source of chirality: diisopropyl d-tartrateAbsolute configuration: (S)