Optically active cyclopropanols from the enzymatic resolution of dimethyl α-alkylsuccinates. Synthesis of chiral 2-vinylcyclobutanones and cyclohexenones.

Enantiomerically Pure Cyclobutane Derivatives and Their Use in Organic Synthesis

“…A β-substituted chiral cyclopropylacrylate ester, 133 , rearranges under Lewis acid catalysis, giving two regiomers of keto esters 134 (70%) and 135 (30%) with high optical purity for the latter (Scheme ). As expected, the major isomer 134 is formed as the result of the preferential migration of the more substituted cyclopropyl carbon 45 …”

“…As expected, the major isomer 134 is formed as the result of the preferential migration of the more substituted cyclopropyl carbon. 101 A general strategy for cyclobutanone formation involves the rearrangement of oxaspiropentanes. 102 These versatile intermediates are readily available by a number of general methods including cyclopropane annulation of ketones and aldehydes, and epoxidation of alkylidene cyclopropanes.…”

The Chemistry of Cyclopropanols

“…A practical method for the preparation of 1-hydroxycyclopropane carboxylic acid 64 , which is used as a convenient starting compound for the synthesis of many cyclopropanol derivatives, is based on the conversion of 1,2-bis(trimethylsiloxy)cyclobutene ( 65) (easily available from succinic esters by acyloin condensation) − into 1,2-cyclobutanedione ( 66) , followed by an acid- or base-induced ring-contraction reaction (Scheme ). − Similar transformations of chiral 2-alkyl-substituted succinic esters allow the preparation of the corresponding optically active 2-methylcyclopropanols. ,,

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“…Thus, for the preparation of (1 R ,2 S )- allo -norcoranamic acid 112 , chiral acetal 113 was used as a precursor. The latter could be prepared in three steps from commercially available ( S )-methyl-2-hydroxymethylpropionate ,, or, alternatively, from dimethyl ( R ) [or ( S )]-2-methylsuccinate. ,, The Strecker reaction of hemiacetal 113 with NaCN and ( S )-α-phenylethylamine leads to the ( S , R )-aminonitrile 114 as a mixture with its ( S , S )-diastereomer (88:12). The major isomer 114 was separated and converted into allo -norcoranamic acid 112 by standard methods (Scheme ) …”