Appeal No. 1996-1959
Application No. 07/946,546
compounds such as the eight and nine-carbon sugar moieties KDO and
KDN are major constituents of non-mammalian tissues.
N-Acetylneuraminic Acid (NeuAc) aldolase, also commonly referred
to as sialic acid aldolase is a type I aldolase known to form an enamine
intermediate with pyruvate, which reversibly reacts with the second substrate
N-acetylmannosamine to give NeuAc…
Neu-Ac aldolase is known to accept many aldoses as acceptor
substrates. In all previously known aldol condensation reactions with such
acceptor substrates, the eneamine [sic] intermediate approaches the si face
of the incoming aldehyde substrate to form a new stereogenic center of S
configuration….
Based on such current knowledge concerning aldolase
stereoselectivity, therefore, NeuAc aldolase is considered to be useful for
only the production of S-sugars having S configuration. As is disclosed
hereinafter, NeuAc aldolase has now unexpectedly been found to be capable
of the production of certain ketoaldonic acids having a formed stereogenic
center of R configuration.
Specification, page 2, line 26 to page 3, line 35.
N-Acetylneuraminic acid (NeuAc) aldolase, is known to accept many aldoses
as acceptor substrates to form stereogenic centers of S configuration. Despite the
recognized stereoselectivity of NeuAc aldolase, Appellants have found that it is
possible to produce ketoaldonic acids having a formed stereogenic center of R
configuration when NeuAc aldolase catalyzes the condensation of pyruvate and
certain five or six carbon L-configured acceptor substrate aldoses (Id., page 4 and
page 9, lines 7-14). The compounds of the present claims have a formed
stereogenic center of R configuration created by the re attack of pyruvate on the
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