RESUMO
Chemo-enzymatic synthesis of lacto-N-biose I (LNB) catalyzed by ß-1,3-galactosidase from Bacillus circulans (BgaC) has been developed using 4,6-dimethoxy-1,3,5-triazin-2-yl ß-galactopyranoside (DMT-ß-Gal) and GlcNAc as the donor and acceptor substrates, respectively. BgaC transferred the Gal moiety to the acceptor, giving rise to LNB. The maximum yield of LNB was obtained at the acceptor : donor substrate ratio of 1:30.
Assuntos
Bacillus/enzimologia , beta-Galactosidase/metabolismo , Acetilglucosamina/análogos & derivados , Acetilglucosamina/metabolismo , Catálise , Glicosilação , Cinética , Estereoisomerismo , Especificidade por SubstratoRESUMO
[Structure: see text] A powerful Ti-crossed Claisen condensation between ketene silyl acetals (KSAs) and acid chlorides was successfully performed to give alpha-monoalkylated esters and thermodynamically unfavorable (less accessible) alpha,alpha-dialkylated beta-keto esters in good yield (46 examples; 41-98% yield). A closely related reaction between ketene silyl thioacetals (KSTAs) and acid chlorides also proceeded smoothly to give alpha-monoalkylated and alpha,alpha-dialkylated beta-keto thioesters (21 examples; 61-97% yield). The present protocol was extended to the direct condensation of KSAs with carboxylic acids (14 examples; 71-97% yield).
RESUMO
Integration of different-period distributed Bragg reflectors (DBRs) is required in constructing an intra-board optical interconnection device with wavelength division multiplexing (WDM). Interference exposure method with cylindrical Lloyd mirror optics and mask aligner was discussed for integrating those DBRs simultaneously. DBRs were designed to give coupling efficiency higher than 80% with coupling length of 0.6 mm and crosstalk noise less than -10 dB with 3 nm wavelength separation for optical interconnection using eight wavelengths around 850 nm. Interference exposure system was developed and integration of eight DBRs by two times exposure was demonstrated.