SUCROSE AS A RENEWABLE ORGANIC RAW-MATERI AL - NEW, SELECTIVE ENTRY REACTIONS VIA COMPUTER-SIMULATION OF ITS SOLUTION CONFORMATIONS AND ITSHYDROXYL GROUP REACTIVITIES
Fw. Lichtenthaler et al., SUCROSE AS A RENEWABLE ORGANIC RAW-MATERI AL - NEW, SELECTIVE ENTRY REACTIONS VIA COMPUTER-SIMULATION OF ITS SOLUTION CONFORMATIONS AND ITSHYDROXYL GROUP REACTIVITIES, Zuckerindustrie, 121(3), 1996, pp. 174-190
This account describes the application-oriented development of novel,
highly selective and practicable ''entry reactions'' for the derivatiz
ation of sucrose, utilizing modem molecular modeling procedures, which
allow the realistic simulation of the preferred conformation in proti
c (water) and aprotic solvents (DMF, pyridine) as well as the differen
t reactivities of the eight hydroxyl groups. Due to the persistence, i
n DMF solution, of a hydrogen bond between the glucose and fructose po
rtions, of the type 2g-O ... HO-1f and 2(g)-O ... HO-3(f), two conform
ations are preferred, of which the MOLCAD-generated electrostatic pote
ntial (MEP) proves the 2(g)-OH the by far most electropositive, i.e. t
he most acidic one and, hence, the one to be deprotonated first. This
insight was transferred into practicable chemistry: deprotonation of s
ucrose in DMF with base (1 molar equiv.) and quenching the monoalkoxid
e with benzyl bromide generates 2(g)-O-Benzyl-sucrose (> 80%) - a new
entry reaction that made readily accessible a series of 2(g)-modified
products: 2-deoxy-sucrose, sucrosamine, sucrose-2,3-epoxide, and enant
iopure dihydropyranone, all compounds with industrial application pote
ntial. - An entry into glucosyl-C-4-modified sucroses is possible via
pivaloylation to the 4(g)-OH-free heptapivaloate (> 50%) which through
oxidation, oximation, reduction, and beta-elimination provides a simi
lar set of new application-profiled products. - Another, highly select
ive entry reaction for the chemical modification of sucrose, and alrea
dy realized on an industrial scale, is the enzymatically induced 2(f)-
O-->6(f)-O-glucosyl shift to isomaltulose - a transformation, that on
the basis of molecular modelings can be readily understood as a closed
shell process. Being more easily derivatizable than sucrose, isomaltu
lose is readily converted into products with industrial application pr
ofiles: air-oxidation generates glucosyl-alpha(1-->5)-arabinonic acid,
reductive amination isomaltamine, each being convertible in one more
step - amidation with fat-amines or N-acylation with fatty acids - int
o products with interesting detergent and liquid crystal properties; a
cidic dehydration transforms isomaltulose into glucosyloxymethyl-furfu
ral (alpha-GMF) in a surprisingly uniform reaction, which - like its p
arent compound HMF - is amenable to various ensuing reactions, e.g. to
alpha-GMF-acrylic acid esters, that, on polymerization, are apt to pr
ovide new, biologically degradable polymers.