- The enantiospecific synthesis of an isoxazoline. A RGD mimic platelet GPIIb/IIIa antagonist
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A convergent, large-scale, chiral synthesis of isoxazoline 1 has been achieved in 37% overall yield and > 99.6% optical purity, starting from L-asparagine and 4-cyanobenzaldehyde. Hofmann reaction of N(α)-n-Boc-L-asparagine with iodosobenzene diacetate provides optically pure N(α)-n-Boc-L-α,β-diaminopropionic acid (8) in 75% yield. A process of lipase resolution-base catalyzed epimerization gives the single enantiomer 5. Reaction of acid 5 with amine 9 in the presence of thionyl chloride forms the framework of 1. A Pinner reaction of intermediate 4 in methyl acetate or anisole, followed by an amidination with ammonium acetate, gives optically pure product 1.
- Zhang, Lin-Hua,Chung,Costello,Valvis,Ma,Kauffman,Ward
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p. 2466 - 2470
(2007/10/03)
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- Rearrangement of Nα-Protected L-Asparagines with Iodosobenzene Diacetate. A Practical Route to β-Amino-L-alanine Derivatives
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A general synthetic method for the Hofmann rearrangement of protected asparagines has been developed. Reaction of asparagine derivatives with iodosobenzene diacetate (PIDA) in mixed solvents produces β-amino-L-alanines in good yield. Advantages over the commonly used reagent bis(trifluoroacetoxy)iodobenzene have been discussed.
- Zhang, Lin-Hua,Kauffman, Goss S.,Pesti, Jaan A.,Yin, Jianguo
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p. 6918 - 6920
(2007/10/03)
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