期刊
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
卷 2007, 期 33, 页码 5590-5602出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/ejoc.200700443
关键词
amino acids; bromine; protecting groups; debromination; oxazolidinones; regioselectivity
N-Boc-protected tyrosine esters 5a,b were converted into tetrahydroisoquinolines 13 and 14 in four steps by reduction and ring closure to oxazolidinones 9 and 10, addition of benzenesulfinic acid and aldehydes to sulfones 11 and 12 and subsequent Lewis acid catalyzed cyclization. In the case of m-tyrosine derivative 5a, selective protection with bromine prevented the formation of undesired regioisomers. Debromination of target compounds 13 was readily achieved under radical reduction conditions by using Bu3SnH/AIBN. Tetrahydroisoquinolines 13 and 14 were isolated as single diastereomers whose trans configuration was confirmed by Xray crystal structure analysis. Partial epimerization of trans-13i and trans-21 to the corresponding cis diastereomers was achieved under basic conditions.
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