Mikio Taniguchi

Aldol reaction of allenolates generated via 1,4-addition of iodide anion or its equivalent to α,β-acetylenic ketones

TMSI, Et2AlI and (n-Bu)4NI/TiCl4 smoothly added to α,β-acetylenic ketones in a 1,4-fashion to yield allenolates 2, which reacted with aldehydes providing aldol adducts in good overall yield. A high Z-stereoselectivity was achieved by use of (n-Bu)4NI/TiCl4 at −78°C, while a high E-stereoselectivity occurred at 0°C.

β-Halovinyl ketones: Synthesis from acetylenic ketones

Abstract The reaction of terminal acetylenic ketones with NaI or LiBr gave almost exclusively E-β-iodo- or E-β-bromovinyl ketones in trifluoroacetic acid, while Z-β-iodo- or Z-β-bromovinyl ketones were the major products in acetic acid. Trimethylsilyl iodide and bromide reacted smoothly with acetylenic ketones at −78°C to give TMS-allenolates which were readily converted to β-iodo- and β-bromovinyl ketones, respectively.

Synthetic approach to the total synthesis of fumitremorgins II synthesis of optically active pentacyclic intermediates and their dehydrogenation

Abstract Optically active pentacycles ( 13–18 ) were synthesized from L- and D-tryptophans, two of which ( 13 and 15 ) were alkylated and dehydrogenated to 21 and 22 , respectively.

Cyclic tautomers of tryptamines and tryptophans. V. Formation and reactions of cyclic tautomers of cyclo-L-tryptophanyl-L-proline ☆

Abstract Two stereoisomeric cyclic tautomers ( 5 and 6 of cyclo-L-tryptophanyl-L-proline whose stereochemistry was established by x-ray analysis, gave 5- and 6-hydroxytryptophanyl derivatives ( 10 ), 11 , and 19 ) on the hydroxylation with lead tetraacetate in trifluoroacetic acid.