No abstract

Enantiomerically pure fluoro-[D1]methyllithium and iodo-[D1]methyllithiums of up to 92% ee were generated by transmetalation of the corresponding stannanes with MeLi in THF at various temperatures. The intermediate halo-[D1]methyllithiums were trapped with benzaldehyde or acetophenone already present in excess in the reaction mixture to either give halohydrins or to disintegrate to carbene. The fluoro-[D1]methyllithiums were found to be microscopically configurationally stable within the tested range of -95 to 0 °C, but chemically only stable at temperatures below -95 °C due to a rapidly increasing portion disintegrating to carbene. The iodo-[D1]methyllithiums were configurationally labile relative to the rate of addition to PhCHO at all temperatures tested (-95 to -30 °C). Disintegration to carbene interfered as well.

Enantiomerically pure (S)-tributylstannyl[D1]methanol and (R)- and (S)-tributylstannyl[D1]methyl benzoates were Stille-coupled with bromobenzene and benzoyl chloride in 1,4-dioxane and toluene using [(Ph3P)4Pd] or [(Ph3P)2PdCl2] either alone or in combination with CuCN as cocatalyst at temperatures up to 80 °C. The products were found to be enantiomerically pure. (R)- and (S)-N-(tributylstannyl[D1]methyl)phthalimides gave enantiomerically pure products with benzoyl chloride, but with bromobenzene protected phenyl[D1]methylamines gave products of only 52–69 % ee depending on the solvent used. Tributyl(thio[D1]methyl)stannanes could not be Stille-coupled with benzoyl chloride or with bromobenzene. Similarly, dimethyl phenyl[D1]methylboronate underwent a Suzuki–Miyaura coupling with bromobenzene to give phenyl[D1]methylsilane with 99 % ee. All couplings followed a retentive course and, except in one case, the intermediate [XCHDPdLn] complexes were found to be microscopically configurationally stable.

Enzymes and chirality are intimately associated. For their mechanisms to be studied, chiral substrates are needed as probes. Here, we report a concise synthesis of (R)- and (S)-[O,O,O]phosphoenol pyruvate starting from enantiomerically pure (R)-2-chloro-1-phenylethanol, which was transformed into O-labeled 3-methyl-1-phenylbutane-1,3-diol. The diol was reacted with tris(dimethylamino)phosphane and consecutively with HO to yield a mixture of cyclic H-phosphonates labeled with O andO. They were silylated and subjected to a Perkow reaction with ethyl 3-chloropyruvate. Two protected-[O,O,O]phosphoenol pyruvates were formed and finally globally deprotected. Their configuration was reassessed by a known enzymatic test in combination with conversion of the formed d-glucose-6-phosphate into mixtures of labeled methyl d-glucose-4,6-phosphates, which were analyzed by P NMR spectroscopy. The enzymatic test supported the configuration assigned to labeled stereogenic phosphorus atoms on the basis of synthesis.

cis-2-Butene-1,4-diol was heated with triethyl orthoacetate and p-hydroquinone as catalyst at 170 °C to give racemic Taniguchi lactone. It was converted into diastereomeric amides with (S)-1-phenylethylamine for stereoisomer resolution. The double bonds of (±)-, (R)- and (S)-Taniguchi lactones were brominated and dehydrobrominated in two steps, using at first DBU and then LDA, to deliver the triple bonds.