Saponification acetate groups

Aldehydes are still used to prepare diuretics (82USP4338435) and antihypertensives (87USP4634689), e.g., when 106 is heated with 6-bromohexanal, thiadiazine 107 (X = Br) results. Substituted sulfonamide 106 can apparently be made from the corresponding disulfonyl chloride by sequential amidation with methylamine and then benzylamine. The presence of the bromine moiety in 107 allows 107 [X = PO-(OH)CH2COOH] to be made by reaction with diethyl carboethoxy-methylphosphonite [(EtO)2PCH2COOEt] and subsequent saponification of the phosphinate and acetate groups. Hence, condensation in trifluo-... 

The complete hydrolysis of the soluble cellulose derivative required gradual addition of water and, preferably, acid. Water can act on cellulose acetate hydrogensulfate in three ways (a) saponification of sulfate groups, (b) saponification of acetate groups, and (c) hydrolysis of glycosidic bonds. Reaction (a) is most rapid and occurs under the mildest conditions. As Table II shows, the product is not any more water soluble (Entries 1-4). Under more severe conditions, the deacetylation (b) has proceeded to water-soluble products, the total amount of dissolved carbohydrates corresponding to theory (Entries 5-10). How-... 

Napieralski cyclization by heating with POCl3 in xylene followed by methanolic workup and saponification of the acetate groups. After selective tosylation of the hydroxyl group at C-2 on 551 usingp-toluenesulfonyl chloride in pyridine, base-induced elimination with DBU in DMSO and hydrolysis of the A, O-acetal with 50% aqueous acetic acid then produced ( )-haemanthidine (382) (2/5). 

The deMayo-type photochemistry of 1,3-dioxin-4-ones has been beautifully applied by Winkler et al. to the synthesis of complex natural products. Substrate 133 gave under sensitized irradiation (with acetone as cosolvent) product 134 as single diastereoisomer (Scheme 6.47). The diastereoselectivity results from cyclic stereocontrol exerted by the two stereogenic centers in the spiro-bis-lactone part of the starting material. After installation of the furan, saponification and bond scission in a retro-aldol fashion generated a keto carboxylic add, which produced the natural product ( )-saudin (135) by simultaneous formation of two acetal groups [128]. 

The acetate group is cleaved without benzyl ether deprotection under mild basic conditions using sodium methanolate in methanol. In this so-called Zemplen saponification, AMBERLITE IR120 is used, which is a gel-type strongly acidic cation-exchange resin of the sulfonated polystyrene type. 

The final stage of the synthesis from lactam 69 required three major operations introduction of the nitrogen atom at C(3), reduction of the C(4) carbonyl, and formation of the C(9) phosphate moiety. The first of these objectives was accomplished by saponification of the acetate group... 

Poly(vinyl acetate) consists of a 1,3-substituted aliphatic backbone with an acetate group at every second carbon atom in the chain. As a result, the polymer surface is hydrophobic and not wetted, swollen, or dissolved by water. However, in alkaline media the acetate groups can be partially or fully saponified to OH groups. The resulting structure is a poly(vinyl acetate-vinyl alcohol) copolymer, which becomes increasingly soluble with increasing degree of saponification. 

In a parallel investigation, the saponification of PVAc was followed by solid-state C-NMR measurements (Fig. 4). The slow reactivity of the PVAc is corroborated by the fact that after 18 hours only 70% of the acetate groups have been hydrolysed and that after 48, when the sample is completely penetrated by water, 20% of the acetate groups are still present. Thus, saponification of the acetate groups, which is a prerequisite for swelling and dissolution in water, is slow and accounts for the low rate of water ingress. 

Osugi [20], Inoue, and Sakurada [21], and Wheeler et al. [22] pointed out that the drop in the DP of polyvinyl acetate by saponification is due to the cutting of branches at the acetyl groups of polyvinyl acetate. The evidence for this mechanism is found in Figure 4.3, where an example of the dependence of the DP of polyvinyl acetate and alcohol on the conversion is shown. 

Quantitative analysis of acetate groups in SRL and SRC samples were performed by a tracer study using l C-labeled acetic anhydride, proton nmr, carbon-13-nmr and saponification of acetate groups, followed by titration of liberated acetic acid. Comparison of results are reported in Table 3. 

The saponification step is accompanied by the disappearance of the photoline of the C=0 carbon of the acetate group at a binding energy of 282.2 eV in the XPS spectrum. In addition, in the IR-ATR spectrum a broad OH stretching vibration band appears at 3410 cm (Fig. 23). According to Clark and Briggs, on subsequent SO2 plasma treatment, sulfate groups are formed [124,125]. SO functions may be incorporated into the poly(vinyl chloride) sequences as well. 

Another carrier polymer is polymer-plasticized poly(vinyl chloride) (PVC/EVACO), which was developed for medical application. Hydroxyl groups as functional groups were created through saponification of the vinyl acetate groups of the EVACO component. 

The grafted polymer poly[(ethylene-co-vinyl acetate-co-carbon monoxide)-graft-vinyl chloride] (PVC/EVACO) known in medical applications as plasticized poly(vinyl chloride) was apphed as a carrier polymer for the covalent immobilization of fibronectin. The surface modifications were carried out on foils both with closed surface structure and with microporous surfaces produced by a phase-inversion technique. The vinyl acetate groups of the carrier polymer were saponified and then reacted with hexamethylene diisocyanate (HDI) as a spacer. Fibronectin is immobilized upon reaction of the free isocyanate group with an amino group of the protein (Fig. 33). The saponification of the carrier polymer was verified by IR-ATR and XPS [149]. The presence of hydroxyhc groups after hydrophihzation is demonstrated by a contact angle of 61° while that of the basic polymer is 110°. 

PVAL is a watersoluble polymer (nonsoluble in organic solvents). PVAL is prepared by partial or complete hydrolysis (sometimes referred to in this case as saponification) of poly (vinyl acetate). The properties of PVAL depend on the residual content of acetate groups. Polymer analogue reactions of aldehydes with PVAL give poly (vinyl acetals) (with butyraldehyde poly (vinyl butyral) with formaldehyde poly (vinyl formal), see Fig. 2.2.2). The copolymer of PVAL and polyethylene is used as barrier polymer against non-polar solvents. 

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