Dextrine

The 5,8-disubstituted indolizidines and 1,4-disubstituted quinolizidines are the more common structural patterns found in amphibian skin[21]. None of these alkaloids has so far been reported from any other source. In addition, the biological activity of only a few 5,8-disubstituted indolizidines has been investigated due to the isolation in minute quantities from the skin. Among them, the relative stereochemistry of quinolizidine 2071 was anticipated to be 75 by our chiral synthesis of 76[35] followed by stereocontrolled synthesis of 75[36]. A sample of synthetic racemate of 75 had produced the best separations on GC analysis with (3-dextrin chiral column[36]. 

We are grateful to Dr. John H. Cardellina, II, National Cancer Institute, Prof. D. John Faulkner, University of California, San Diego, and Prof. Raymond J. Andersen, University of British Columbia, for kindly providing us with H, l3C NMR spectra of natural clavepictines A, B, Pictamine, and lepadin B. We are also indebted to Dr. Thomas F. Spande, National Institute of Health, for measurement of the GC analysis of synthetic, racemic, and natural quinolizidine 2071 with (3-dextrin chiral column, and to Prof. Andre Rassat, Ecole Normale Superieure, for kindly providing us with racemic quinolizidine 2071. 

The enzymes that hydrolyze (1 — 6)-a-D-glucosidic linkages in starch and glycogen and in related a- and /3-dextrins are called debranching enzymes. The nomenclature for this type of enzyme was confusing, but has been clarified. 

The plant and bacterial enzymes capable of hydrolyzing pullulan do not have identical specificities. In particular, the plant enzymes have little or no action on glycogen and phytoglycogen under conditions in which they readily hydrolyze amylopectin and its /3-dextrin. To stress this difference (the bacterial enzymes are capable of degrading both glycogen and phytoglycogen), Manners (1997) recommended different nomenclature for bacterial enzymes, to be called pullulanase, and the plant enzymes, to be called limit dextrinases. 

D-Glucitol, dulcitol, L-perseulose, n-perseulose, Schardinger /3-dextrin, (levo)-malic acid Raffinose Xylitol... 

When a /3-dextrin is broken up by the a-amylase into a-dextrins, the a-dextrins, in contradistinction to the /3-dextrin itself, are attacked by the /3-amylase with the liberation of fermentable sugar (Table XlII). This means that when maltose linkages in the interior chains of the /3-dextrin are broken by the a-amylase, anomalous a-dextrins are formed, the normal end chains of which are saccharified by the 8-enzyme (see Fig. 5, page 276). 

Most amylases have only a slight action on the phosphate groups. As mentioned before, the 3-dextrin from potato starch contains all the phosphorus of the starch. This is in accordance with the fact that the phosphorus is concentrated in the amylopectin. A /3-dextrin from arrow-root starch had a phosphorus content of 0.051 % while the starch itself had 0.019%. Since the /3-dextrin corresponds to 40% of the starch, it is evident that here also all the phosphorus is left in the /3-dextrin. 

Isolation, empirical formula of /3-dextrin ( cellu-losine ) from crude bacterial digest of starch Isolation of a- and -dextrine Isolation of Bacillus macerans Empirical formula of a-dextrins a-Dextrin series diamylose, tetraamylose, hexa-amylose -dextrin series triamylose, hexa-amylose a-diamylose ... 

The simplest means of distinguishing the a and /3 dextrins is the iodine reaction. Crystalline a-dextrin-iodine complex in thin layers is blue when damp, gray-green when dry the crystalline /3-dextrin-iodine complex is brownish (red-brown) damp or dry. 

Fig. 5.—Rotational changes during hydrolysis in 51% sulfuric acid. 1, Starch 2, Qi-dextrin 3, /3-dextrin 4, maltose 5, 1,6-anhydromaltose 6, levoglucosan.

Schardinger recognized only the a and /3 dextrins. Freudenberg definitely obtained the 7 dextrin and raised the possibility that higher homologs exist, though it is doubtful whether the 5-dextrin and t-dextrin fractions represented the homologous 9- and 10-membered saccharides. 

Fig. 8.—Rotational changes during acetolysis. 1, Tri-O-aeetylstarch 2, a-o-glu-cose pentaacetate 3, a-dextrin triacetate 4, /3-dextrin triacetate 5, y-dextriii triacetate 6, hexa-0-acetyl-l,6-anhydromaltose.

O. 3-dextrin acetate (40 g.) with traces of s-dextrin acetate... 

To refine purified /3-dextrin further, it may be dissolved in water (about a 2 % solution) at room temperature and allowed to stand a considerable time in order to promote aggregation of insoluble impurities and complexes. After filtration through a fine fritted-glass filter, the solution should be concentrated to about one tenth of the original volume and allowed to crystallize. 

Purified 7-dextrin is handled in much the same fashion as is a-dextrin, except that toluene may be used as the specific precipitant. Crystallization from 60% 1-propanol should be repeated until there is no evidence for /3-dextrm in the mother liquors (when allowed to crystallize on a microscope slide). The /3-dextrin crystallizes with ease from the mixture, and it can be recognized by its characteristic crystal form (see Fig. 3). 

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