Biocatalytical Transformations, III [1] Regioselective Enzymic Deacetylations of Laevoglucosane Triacetate

Abstract

<jats:title>Abstract</jats:title><jats:p> Several hydrolytic enzymes (porcine liver esterase, lipase from wheat germ type I, and the lipase from rhizopus javanicus) efficiently deacetylate laevoglucosane triacetate (2) with good regioselectivity into diacetylated laevoglucosane derivatives (3-5).</jats:p>

Enzymatic Protecting Group Techniques

“…Therefore, the directed manipulation of their hydroxyl groups is of particular interest. Each of the three OH groups in 1,6-anhydroglucopyranose can be liberated selectively, making use of enzymatic reactions (Figure , Table ). − , Thus, from the triacetate 127a , the 4-protecting group was split off using lipase from porcine pancreas (PPL) 209 or pig liver esterase (PLE). , The acetate in the 3-position could be attacked preferentially using chymotrypsin 209 or lipase from wheat germ (WGL), and the 3,4-diacetate 135 was obtained by hydrolysis with lipase from Rhizopus javanicus (RJL) . In each case, however, other derivatives were formed as undesired byproducts.…”

“…[208][209][210]212 Thus, from the triacetate 127a, the 4-protecting group was split off using lipase from porcine pancreas (PPL) 209 or pig liver esterase (PLE). 208,209 The acetate in the 3-position could be attacked preferentially using chymotrypsin 209 or lipase from wheat germ (WGL), 208 and the 3,4-diacetate 135 was obtained by hydrolysis with lipase from Rhizopus javanicus (RJL). 208 In each case, however, other derivatives were formed as undesired byproducts.…”

Enzymic Protecting Group Techniques

“…Thus, from the triacetate 75 the 4-protecting group was split off using lipase from porcine pancreas (PPL)95 or pig liver esterase (PLE).95 '96 The acetate in the 3-position could be attacked preferentially using chymotrypsin95 or lipase from wheat germ (WGL),96 and the 3,4-diacetate 81 was obtained by hydrolysis with lipase from R. javanicus (RJL). 96 In each case, however, other derivatives were formed as undesired byproducts. High yields could be obtained by employing the tri-n-butanoate 76. It was converted to the 2,3-dibutanoate 78 in 91% yield by means of several lipases, but the enzyme from C. cylindracea (CCL) removed two acyl groups from 76 successively to yield the monobutyrate 79.94 Similarly, the 3-azido-1,6-anhydropyranose 82 is regioselectively deacylated at 0-2 and 0-4 by means of alcalase and lipase OF from C. cylindracea, respectively.98 Of particular importance is the stereochemistry at C-4 of the bicyclic substrates.…”

Σύνθεση Νέων Αναστολέων Φωσφολιπασών Α2 Και Μελέτη Της Αντιφλεγμονώδους Δράσης Τους

“…Μια θηλιά που περιλαµβάνει µια µακριά έλικα, δηµιουργεί τη σύνδεση µε το β 4 κλώνο στο κεντρικό µέρος της πτυχής. Ο επόµενος παράλληλος κλώνος β 5 περιέχει την καταλυτική σερίνη (228). Τρεις ακόµα α έλικες διαπλεκόµενες µε θηλιές εξασφαλίζουν τη σύνδεση ανάµεσα σε αυτή την περιοχή και τους πιο αποµακρυσµένους β κλώνους (β 6-β 9).…”

“…Κάθε ένα από τα τρία υδροξύλια στην 1,6-ανυδρογλυκοπυρανόζη µπορεί να απελευθερωθεί εκλεκτικά, κάνοντας χρήση ενζυµικών αντιδράσεων. Έτσι, από το τριακετυλο-παράγωγο 118α, η 4-προστατευτική οµάδα διασπάστηκε µε τη χρήση χοίριας παγκρεατικής λιπάσης (PPL)227 ή της εστεράσης PLE 227,228. Η ακετυλοµάδα στην 3 θέση µπορεί κατά προτίµηση να προσβληθεί χρησιµοποιώντας λιπάση WGL.…”