A CONCISE TOTAL SYNTHESIS OF (-)-CIS-CLAVICIPITIC AND (+-)-TRANS-CLAVICIPITIC ACIDS BY COMBINATIONAL USE OF DIRECTED LITHIATION AND FLUORIDE ION-INDUCED ELIMINATION-ADDITION REACTION OF 1-(TRIISOPROPYLSILYL)GRAMINE DERIVATIVES()
M. Iwao et F. Ishibashi, A CONCISE TOTAL SYNTHESIS OF (-)-CIS-CLAVICIPITIC AND (+-)-TRANS-CLAVICIPITIC ACIDS BY COMBINATIONAL USE OF DIRECTED LITHIATION AND FLUORIDE ION-INDUCED ELIMINATION-ADDITION REACTION OF 1-(TRIISOPROPYLSILYL)GRAMINE DERIVATIVES(), Tetrahedron, 53(1), 1997, pp. 51-58
A six-step total synthesis of (+/-)-clavicipitic acid (1) from 1-(trii
sopropylsilyl)gramine (2) was achieved by combinational use of 4-selec
tive lithiation of 2 and fluoride ion-induced elimination-addition rea
ction of -hydroxy-3-methyl-1-butenyl]-1-(triisopropylsilyl) (7) as key
reactions. Separation of cis- and trans-diastereomers (1a and 1b) wer
e easily accomplished by simple fractional crystallization and column
chromatography. The overall yields of 1a and 1b from 2 were 21% and 17
%, respectively. Copyright (C) 1996 Elsevier Science Ltd