A shortened synthesis of optically pure tricarbonyl(methyl 6-oxo-2,4-hexadienoate)iron leading to improved yield

William A Donaldson,Sergey Lindeman,Rajesh K Pandey,Joachim Schantl

doi:10.3998/ark.5550190.0011.404

Abstract

A shortened synthesis of optically pure tricarbonyl(methyl 6-oxo-2,4-hexadienoate)iron leading to improved yield

Highlights

Planar chiral organometallic complexes have found widespread use in asymmetric organic synthesis.[1]
We reported a 5-step route from (R)-glyceraldehyde acetonide, which gave (+)-1 and (–)-1 (15% and 21%, respectively),[4] and we have utilized this route to these planar chiral scaffolds for the synthesis of the C9–C16 segment 2 of ambruticin and 2-(2’-carboxycyclopropropyl)glycine 3.5 We report a shortened synthesis leading to improved yields of the enantiomers of 1, which relies on asymmetric dihydroxylation as the source of chirality
Spectrograde solvents were used without further purification with the exception of anhydrous methylene chloride, which was purchased from Aldrich. (Methoxycarbonylmethylene)triphenylphosphorane (95%) and 2,4-hexadienal were purchased from Avocado Research Chemicals/Alfa Aesar and Acros Organics, respectively

Summary

Introduction

Planar chiral organometallic complexes have found widespread use in asymmetric organic synthesis.[1]. Abstract The (+)- and (–)-enantiomers of tricarbonyl[methyl (2E,4E)-6-oxo-2,4-hexadienoate]iron are prepared in 4 steps from commercially available hexadienal (26% and 25% yields, respectively). Asymmetric dihydroxylation of 6 using commercially available AD-mix β proceeded exclusively at the double bond most remote to the electron withdrawing ester substitutent to afford (2E,4E,6R,7R)-methyl 6,7-dihydroxyocta-2,4-dienoate 7 as a solid.[6] Analysis of the (R,R)- and (S,S)-bis-MTPA esters (8 and 9, respectively) by 1H NMR indicated that each was >94% de.

Results

Conclusion