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Sizing mechanism of alkylketene dimers Part 1. Possibility for AKD to form P-ketoesters in papersheets Akira Isogai. Ryu Taniguchi, Fumihiko Onahe and Makoto U.suda, Department of Forest Products, Faculty of Agriculture, The University of Tokyo, Japan Keywords: Sizing, Alkylketene dimers, Cellulase. Extraction, Cellulose, Amorphous. P-Ketoesters, Retention. SUMMARY: The possibility for alkylketene dimer (AKD) to form P-ketoesters with hydroxyl groups of cellulose andlor hemicellulose in pulp fibers during papermaking and condition- ing processes was

.DEGWHOS, BINAP, BJPHEMP etc. These catalysts are very efficient for the production of optically pure (>W%) p-hydroxy esters from the corresponding P-ketoesters (1 5 ) which are converted, with formaldehyde, into the corresponding dioxanones U. The electrophilic amination of these derivatives proceeded smoothly with di-ter- azodicarboxylate and furnished the anti diastereoisomers Ifi, 16.12 in good to excellent yields as shown in scheme 4. @ 1996 IUPAC, Pure and Applied Chemistry 68, 593-596 Asymmetric synthesis of /3-hydroxy a-amino acids 595 Scheme 4 Electrophilic

of residual lignin in 3:144 Turunen, E. chemical pu1ps.-Part 2. Puri- Sundqtrist, J. fication and characterization of residual lignin after enzymatic hydrolysis of pulps Isogai, A. Sizing mechanism of alkylketene Taniguchi, R. dimers.-Part 1. Possibility for AKD 4:193 Onahe, F. to form P-ketoesters in papersheets. Usuda, M. -Part 2. Deterioration of alkyl- 4:205 ketene dimer emulsion Lachenal, D. Degradation of residual lignin in 1: 25 M~rguet, M. kraft pulp with ozone. Application to bleaching Lindholnz, C.-A. Alkaline extraction of ozone- 2: 95

hydroxyl groups of cellulose and hemicellulose in pulp fibers during papermaking and conditioning treatments has been reported as one mechanism for the appearance of the sizing features (Davis et al. 1956: Dumas 1981; Lindstrom, Soderberg 1986; Lindstrom, O'Brian 1986; Nahm 1986; 0dberg et al. 1987; Marton 1990, 1991). On the other hand, some reports showed that AKD may not form such pketo- esters under the usual conditions of papermaking or conditioning, and that sizing features of AKD might be explained in terms of mechanisms other than the P- ketoester

-HIV agent carbovir (7).10 A transamidation process can be used for the conversion of pig insulin into human insulin. This represented the first example of a biotransformation being employed to provide a compound for use in the clinic.11 Reduction of ketones to chiral secondary alcohols using microorganisms and dehydrogenase enzymes is well researched and often the stereochemistry of the product(s) from such a reductive biotransformation can be predicted. Simple acyclic dialkylketones, P-ketoesters and P-diketones are reduced to give secondary alcohols, P

obtaining five-membered rings and for opening strained-rings, but we did not know if this reaction was able to produce six-membered rings.To have an answer to this question €,a-unsaturated-p-ketoesters were synthetized and irradiated in the presence of triethylamine. Compound U was transformed into two bicyclic products 18 and Le with a yield of 65%; The major isomer was the one where the methyl and the hydroxy groups were in a trans relative position (ref. 19). 17 COZM t) C02M e 1 8 1 9 1886 J. COSSY As six-membered rings were obtained easily from €,a

cycloaddition of the enamine to the 2-azadienes (the stereochemistry of the products has not been established). v C O p M e Y O n M e MeYN - vNH AcopMe Me kNH COpR - COpR C0pR 15 Scheme4 /+c02Me vo2Me vco2Me NH R 0 2 C T N H M e O C y N H Me Me 17 IS 19 Me Scheme 5 A C 0 2 M e The thiazolidines derived from the reactions of P-ketoesters and 1,3diketones also gave stable bis(enamines) upon treatement with silver carbonate and DBU. For example, the thiazolidines 17 formed from ethyl acetoacetate and methyl acetoacetate gave the bis(enamines) 18 and compound

between carboxymethylated pulp and PAE. Therefore, as we reported previously, nearly no (3-ketoesters may be pre- sent in AKD-sized paper prepared under usual condi- tions, where sufficient sizing features appear on the AKD-sized paper. Anyway, since quantitative analysis of p-ketoesters can not be achieved by solid-state "C- NMR as long as the cross polarization technique is adopted, subtle changes in sizing features of AKD- sized papers prepared under various conditions could not be studied in terms of subtle changes in the amount of (3-ketoesters present

. For example, support-bound imines can be easily formed by condensation of immobilized aldehydes with large excesses of amines; reaction of these imines with acid chlorides in a Staudinger condensation leads to very efficient p-lactam formation (29).[ 161 Similarly, in a modified Biginelli condensation, reaction of this aldehyde with guanidines (and amidines) and P-ketoesters efficiently leads to dihydropyrimidines (25 to 28).[ 171 Reaction with /3-ketoesters and amines gives the dihydropyridines 26,[ 181 while condensation with amines and a-diketones affords

conversion is regulated by stirring time. The organic products are easily separated by simple decantation and the aqueous phase containing the catalyst can be recycled. The excellent regioselectivity, the easy recovery and recycling of the aqu2ous rhodium catalyst permits industrialization to produce intermediates for vitamin E like geranylacetone in a short and economical process compared to the old chemistry which uses a more expensive raw material like linalool [Fig. 71 ; Futhermore the intermediate P-ketoester C, is also a key compound to pseudoionone and vitamin