Synthesis of the 2-Alkenyl-4-alkylidenebut-2-eno-4-lactone (=α-Alkenyl-γ-alkylidenebutenolide) Core Structure of the Carotenoid Pyrrhoxanthin via the Regioselective Dihydroxylation of Hepta-2,4-diene-5-ynoic Acid Esters
✍ Scribed by Joachim Schmidt-Leithoff; Reinhard Brückner
- Book ID
- 102261007
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- German
- Weight
- 338 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
A new strategy for the stereoselective synthesis of 4‐alkylidenebut‐2‐eno‐4‐lactones (=γ‐alkylidenebutenolides) with (Z)‐configuration of the exocyclic CC bond at C(4) was developed. It is exemplified by the synthesis of 4‐alkylidenebutenolactone 31 (Scheme 4), which constitutes a substructure of the carotenoids pyrrhoxanthin (1) and peridinin. The formation of the precursor 4‐(1‐hydroxyalkyl)butenolactone 29 was accomplished either by cyclocarbonylation of the prop‐2‐yn‐1‐ol moiety of 27 (→29) or by hydrostannylation of the isopropylidene‐protected alkynoic acid ester 26 (→28) followed by transacetalization/transesterification (→30). The 4‐alkylidenebutenolactone was formed by the anti‐selective Mitsunobu dehydration 29→31.