Imino compounds, purification

An amidrazone (58) derived from 5-amino-5-deoxy-L-fuconolactam was found to inhibit a recombinant human a-L-fucosidase with a K -value of 820 nmol/1 [ 111 ]. A simple synthesis of 1,5-dideoxy-1,5-imino-D-arabinitol (59), previously prepared by Ganem et al. [49] as a potential maimosidase inhibitor, was applied to the affinity purification of a-L-fucosidase from bovine kidney by an improved method and the characterization of the enzyme thus obtained [112]. The relatively low affinity of this compound to the enzyme (Kj 2.2 pmol/1 at pH 7) compared to 1-deoxyfuconoJirimycin (51) turned out to be advantageous in terms of enzyme recovery and yield. Structurally related, suitably protected 5-amino-5-deoxy-D-arabinopyranose (60), was coupled with a N-acetyl-6-deoxy-6-thio-D-glucosaminide (61) to give a stable thioglycoside (62) [113]. 

Shin was unable to observe enamino-imino tautomerism in the case of dehydrovaline compounds (253, 373). E. Ohler and U. Schmidt (287, 350) were able to convert a-iminocarboxylic acid esters into a-enaminocarboxylic acid esters (42) by preparing the hydrochlorides of the former, which slowly rearranged into the hydrochlorides of the latter. This reaction is the simplest means of preparing a-enaminocarboxyhc acid esters, as the a-iminocarboxylic acid esters obtained by N-chlorina-tion/dehydrochlorination of amino acid esters can be rearranged directly, without intermediate purification. 

---