Concise Synthesis of All Stereoisomers of β-Methoxytyrosine and Determination of the Absolute Configuration of the Residue in Callipeltin A
摘要:
All stereoisomers of beta-methoxytyrosine (beta-OMeTyr), a stereo-undefined component of callipeltin A, were synthesized from L- and D-tyrosine. The stereochemistry of beta-OMeTyr in callipeltin A was determined to be 2R,3R by an oxidative procedure and Marfey's analysis.
Complete Stereochemistry of Neamphamide A and Absolute Configuration of the β-Methoxytyrosine Residue in Papuamide B
摘要:
[GRAPHICS]The absolute stereochemistry of the three unresolved structural components in neamphamide A (1) was determined to be (R)-beta-methoxy-L-tyrosine, (2R,3R,4S)-4-amino-7-guanidino-2,3-dihydroxyheptanoic acid, and (2R,3R,4R)-3-hydroxy-2,4,6-trimethylheptanoic acid. Stereochemical assignments were made by chemical degradation of 1, derivatization of the resulting products, and then spectroscopic and chromatographic comparison of the derivatives with synthetically prepared standards. Using the same analytical protocol developed for 1, the beta-methoxytyrosine residue in papuamide B (2) was found to be (R)-beta-methoxy-D-tyrosine. This represents a rare example of divergent stereochemistry in an unusual amino acid residue that is present in two closely related classes of peptides.
An Efficient Synthesis of Enantiopure (2R,3R)-β-Methoxytyrosine
作者:Long Jin、Shou-xin Liu、Shi-Ming Fan、Xia Tian、Yi-Hua Yang
DOI:10.1055/s-0034-1381048
日期:——
Enantiopure (2R,3R)-β-methoxytyrosine was stereoselectively synthesized from ethyl 3-(4-hydroxyphenyl)-3-oxopropanoate protected by 2- methoxyethoxymethyl (MEM) (ee >98%). l -Aminoacylase-catalyzed resolution of the corresponding erythro-N-acetyl derivatives afforded (2S,3S)-(4-MEM)-β-methoxytyrosine (ee >99%). The conversion increased to 98% by optimizing the synthesis to yield enantiopure N-acetyl-(2R