Studies Towards the Synthesis of the C(9)-C(20) Lactone-Dipropionate Fragment of Calyculin C

Abstract

In this paper we describe the synthesis of a diastereomer of the C(9)-C(20) dipropionate-lactone fragment of Calyculin C. A short and enantioselective synthesis of the key intermediate 2 has been developed. This intermediate will play a critical role also in the synthesis of the correct diastereomer of C(9)-C(20) dipropionate-lactone fragment of Calyculin C.

Key words

aldol reactions - diastereoselectivity - dihydroxylations - natural products - stereoselective synthesis

References

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6

The separation of lactone or its derivatives (acetylated or benzylated lactone) were not successful with HPLC, but after methylation and reduction, the enantiomers of 12 were separable (Daicel AS column, 10% IPA-hexane, 0.5 mL/min, λ = 254 nm, retention times: 29 min and 39 min) and the ee was checked at this point.

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Data collection with Enraf-Nonius kappa-CCD at 173.0(1) K, MoK_α radiation, λ = 0.71073 Å, triclinic, space group P-1, with a = 6.1216(4), b = 8.7954(8), c = 14.7365(14) Å, α = 100.224(3)°, β = 99.362(4)°, γ = 91.071(7)°, V = 769.52(11) ų, Z = 2, 278 parameters, R 1 = 0.0405, wR2 = 0.0838. CCDC 212408 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB21 EZ, UK; fax: [phone]; or e-mail: [e-mail]).