Nonproteinogenic amino acids: An efficient asymmetric synthesis of (S)-(-)-acromelobic acid and (S)-(-)-acromelobinic acid
An efficient synthesis of (S)-(-)-acromelobic acid (1) and (S)-(-)-acromelobinic acid (2) is described via asymmetric hydrogenation protocol. Asymmetric hydrogenation of dehydroamino acid derivative 23 using (R,R)-[Rh(DIPAMP)(COD)]BF4 catalyst followed by removal of the protective groups afforded (S)-(-)-acromelobic acid (1) in >98% ee. The key intermediate 23 was prepared from citrazinic acid (8). The dehydroamino acid derivative 33 required for the synthesis of (S)-(-)-2 was prepared from 2,5-lutidine (27), which upon hydrogenation using (S,S)-[Rh(Et-DuPHOS)(COD)]BF4 catalyst afforded (S)-(+)-34 in 93% yield and >96% ee. Removal of protective groups in (S)-(+)-34 afforded (S)-(-)-acromelobinic acid (2) in good overall yield.
Adamczyk, Maciej,Akireddy, Srinivasa Rao,Reddy, Rajarathnam E
p. 6951 - 6963
(2007/10/03)
Asymmetric synthesis of (S)-(-)-acromelobinic acid
A total synthesis of (S)-(-)-acromelobinic acid 2, which was isolated from clitocybe acromelalga, was achieved via an asymmetric hydrogenation protocol. Dehydroamino acid derivative 12 was prepared from 2,5-lutidine 5 and subjected to asymmetric hydrogenation using (S,S)-[Rh(Et-DuPHOS)(COD)]BF4 to give the (S)-(+)-pyridylalanine derivative 13 in 93% yield and >96% e.e. Removal of the protecting groups in (S)-(+)-13 afforded (S)-(-)-acromelobinic acid 2.
Adamczyk, Maciej,Akireddy, Srinivasa Rao,Reddy, Rajarathnam E.
p. 2385 - 2387
(2007/10/03)
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