ChemInform Abstract: Asymmetric Synthesis of Cyclopropane-1,1-dicarboxylates from a γ-Alkoxy-alkylidenemalonate.
Abstract
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ChemInform Abstract
Cyclopropanation of the D-mannitol derived alkylidenemalonate (III) with 2-lithio-2-sulfonyl- and 2-lithio-2-nitropropane (IV) provides the same diastereomer (V) from both reagents, however with different diastereoselectivity. On the other hand, formation of the open chain derivatives (VI) and (VII) occurs with almost completely different face-selectivity. Thus, whereas open chain derivative and the cyclopropane arise from the same face of (III) from (IVa), they results from a different face of attack for (IVb). The reason for this discrepancies are unclear.
