SYNTHESIS OF CONFORMATIONALLY RESTRAINED, BETA-SUBSTITUTED DERIVATIVES OF L-TRYPTOPHAN VIA LEWIS ACID-CATALYZED REACTION OF 2,3-AZIRIDINO-BETA-D-LYXO-FURANOSIDES WITH 1-(TRIALKYLSILYL)INDOLES

Reaction of 1-(triisopropylsilyl)indole (or its 5-benzyloxy derivative ) with tert-butyldimethylsilyl oxycarbonyl)-2,3-aziridino-2,3-dideoxy- 5-O-methyl- (or benzyl-)-beta-D-lyxofuranoside in the presence of boro n trifluoride etherate gave, regio-and stereospecifically, the corresp onding protected 2-amino-3-(3-indolyl)arabinofuranoside derivatives. T hese could be transformed, after desilylation, oxidation and removal o f the Boc group, into 2-amino-3-(3-indolyl)arabinonolactone derivative s. The latter represent novel examples of conformationally restrained analogues of L-tryptophan as well as precursors of optically pure beta -substituted L-tryptophans.