The iodolactone approach to enantiopure oxiranes of constrained chiral cyclic β-amino acids

A simple and efficient method has been developed for the synthesis of enantiopure epoxide derivatives of some constrained chiral cyclic β-amino acids via iodolactonization and alkaline de-iodation. Lower stereoselectivities were observed when the classical method using mCPBA was used when a bicyclic β-amino acid was involved leading to a quasi-inseparable mixture of two epoxides.

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8-(Benzyloxcarbonylamino)-2-iodo-6-oxabicyclo[3.2.1]octen-7-oneDe = 99%[α]D = +57 (c 0.8, CH2Cl2)Absolute configuration: (1R,4R,5R,8R)

7-(Benzyloxcarbonylamino)-2-iodo-4-oxa-8-tricyclo[4.3.1.03,7]decan-5-oneDe = 99%[α]D = −55 (c 0.9, CH2Cl2)Absolute configuration: (1R,2R,3R,6R,7R)

8-(Benzyloxcarbonyl)-2-iodo-4-oxa-8-azatricyclo[4.3.1.03,7]decan-5-oneDe = 99%[α]D = +43 (c 1.0, CH2Cl2)Absolute configuration: (1S,2R,3R,6R,7S)

1-(Benzyloxcarbonylamino)-2-hydroxy-3-iodobicyclo[2.2.2]octane-6-carboxylic acidDe = 99%[α]D = −30 (c 0.8, CH2Cl2)Absolute configuration: (1R,2R,3R,4R,6R)

8-(Benzyloxcarbonylamino)-3,4-epoxycyclohexane-1-carboxylic acidDe = 99%[α]D = +71 (c 0.7, EtOH)Absolute configuration: (1R,2R,3R,4S)

1-(Benzyloxcarbonylamino)-2,3-epoxybicyclo[2.2.2]octane-6-carboxylic acidDe = 99%[α]D = −47 (c 0.5, CH2Cl2)Absolute configuration: (1R,2R,3S,4R,6R)

2-(Benzyloxcarbonyl)-2-azabicyclo[2.2.2]oct-5-ene-7-carboxylic acidDe = 99%[α]D = −104 (c 1.2, EtOH)Absolute configuration: (1S,4S,5S,6R,7R)