Enzymes in organic synthesis

Abstract

Immobilized glucose dehydrogenase from Bacillus sp. was found to be a practical catalyst for NAD (P) H regeneration. It is very stable at high temperatures. Coupled with an appropriate alcohol dehydrogenase, several compounds can be prepared in high optical purity. Fructose diphosphate aldolase and glucose isomerase were used in the preparative enzymatic synthesis of several unusual hexoses and ketoses. The aldolase accepts a variety of aldehydes. The combined enzymatic process allowed the synthesis of 5-deoxy-, 6-deoxy-, 6-deoxy-6- fluoro-, and 6-0-methyl hexoketoses and -hexoaldoses. Immobilized N-acetyl neuraminic acid aldolase was shown to be a highly stable enzyme. The enzyme accepts a wide variety of aldoses as a substrate. N-acetyl neuraminic acid was prepared enzymatically on a large scale, whereas 9-0-acetyl-N-acetyl neuraminic acid was prepared on a small scale. Several methyl hexopyranosides and pentofuranosides were selectively deprotected at the primary hydroxyl group by a lipase catalyzed hydrolysis. Peracetylated hexopyranoses and pentafuranoses were selectively cleaved at the anomeric carbon by lipase catalyzed hydrolysis. The selective acetylation of pentafuranoses in THF in the presence of lipase was investigated. The substrate specificity of glucose dehydrogenase from Bacillus sp. was investigated. It accepts a wide variety of aldoses. Nojirimycin is oxidized by the enzyme to the corresponding lactam. None of the tested substrates were found to act as inhibitors. Glucose-6-phosphite was synthesized and fully characterized. It was found to be a substrate for glucose6-phosphate dehydrogenase from yeast. The stability of NADH increased more than twofold in the presence of glucose-6-phosphite as compared to glucose-6-phosphate. Glucose-l-phosphite was prepared and was not accepted by phosphoglucomutase as a substrate nor did it inhibit the isomerization of glucose-l-phosphate