Enzyme-Catalyzed Synthesis of O-Glycopeptide Building Blocks

Abstract

In 1988, MOSBACH et aL¹ reported the synthesis of a-D-mannopyranosy1-L-serine and Q -D-N-acetylgalactosamino-L-serine by reversing the hydrolytic activity of a -mannosidase from jack beans and a -N-acetylgalactosaminidase from beef liver, respectively. The yields in these equilibrium-controlled syntheses² using high concentrations of monosaccharide and serine were highly dependent on the enzyme concentration and ranged from 5 to 10 percent in both cases.     

Synthesis of azidochloromethane and azidobromomethane

By treatment of tris(azidomethyl)amine with dry hydrogen halide, azidochloromethane and azidobromomethane were prepared. The former product, which is more stable than the latter, was isolated as a colorless liquid. The desired azidohalomethanes are intermediates in the nucleophilic substitution of dihalomethanes to generate diazidomethane but could not be detected in this transformation.     

2‐Hydroxytorularhodin,a New Xanthophyll from the Red Yeast Sporobolomyces coprosmae

A new hydroxylated carotenoic acid was isolated from the red yeast Sporobolomyces coprosmae and unambiguously identified as 2‐hydroxytorularhodin ( 1 ), i.e., (all‐E)‐3′,4′‐didehydro‐2‐hydroxy‐β,ψ‐caroten‐16′‐oic acid, by application of extensive 1D and 2D NMR techniques (gCOSY, gHSQC, gHMBC, DQS, gTOCSY, and ROESY). Hydroxylation of carotenoids at C(2) is uncommon in nature, very rare in fungi, and unprecedented for torularhodin.