20
rings, i.e., five and six, respectively, using a cryoscopic method were incorrect. The
correct values were determined by French using both X-ray diffraction and crystal
density measurements.
Between 1942 and 1965, French also contributed greatly to the molecular structural knowledge of the Schardinger dextrins, or, as he preferred to call them,
cycloamyloses (Caesar 1968; Szejtli 1998; Crini 2014). Very quickly, French
became a pioneer in the understanding of their structure, publishing an impressive
number of results on cycloamyloses which are still used as references today (French
and Rundle 1942; Rundle and French 1943; Bates et al. 1943; French et al. 1948,
1949a, b, 1950a, b, 1954; French and McIntire 1950; Norberg and French 1950;
French 1957a, b, 1960, 1962; Bailey and French 1957; Thoma and French 1958,
1959, 1960, 1961; James et al. 1959; Thoma et al. 1959; Whelan et al. 1960; Pulley
and French 1961; Robyt and French 1964; French and Abdullah 1965; French et al.
1963, 1965). French’s first work concerned the molecular weights of the Schardinger
dextrins, considered as cyclic molecules in agreement with the previous results published by Freudenberg (Freudenberg and Meyer-Delius 1938; Freudenberg et al.
1938). French and Rundle (1942), using the X-ray diffraction technique and crystal
density measurements, determined the molecular weights of α-dextrin and β-dextrins
and discovered the exact number of glucose units per dextrin, i.e., six and seven,
respectively, in disagreement with the results published by Freudenberg and Jacobi
(1935). French and Rundle demonstrated that molecular weights were integral multiples of the value 162.1 for a glucose residue. They concluded that the X-ray diffraction technique was better suited to the determination of the molecular weights
of high molecular weight crystalline substances since impurities, such as solvent of
crystallization and inorganic ash, were of minor importance (French and Rundle
1942). In this paper, French also suggested that Schardinger dextrins were cyclic
“macromolecules,” formed from starch polysaccharide (French and Rundle 1942).
They were non-reducing “D-glucopyranosyl polymers” containing 6, 7, or 8 units
linked by α-D-(1→4) bonds, in agreement with the results published by Karrer
(1923) and Miekeley (1932). In each cycloamylose “macromolecule,” the D-glucose
units were in the C1 conformation. Schardinger dextrins were then regarded as cylinders (French and Rundle 1942). However, Freudenberg did not agree with this
point of view (Freudenberg 1943).
French pointed out three interesting features: (1) as a consequence of the C-1
conformation of the glucopyranose units, all the secondary hydroxyl groups were
located on one side of the cylinder, whereas all the primary hydroxyl groups were
located on the opposite side of the cylinder; (2) the interior of the cylinder consisted
only of a ring of C-H groups, a ring of glucosidic oxygens, and another ring of C-H
groups; and (3) the interior of the cavity was relatively apolar compared to water
(French and Rundle 1942; Rundle and French 1943; Bates et al. 1943; French et al.
1948, 1949a, b). Freudenberg claimed again that all the structural and conformational conclusions of French were ambiguous due to “the use of products that were
not pure” (Freudenberg et al. 1947a, b). One year later, Freudenberg and Cramer
concurred with French’s results, after studying the X-ray measurements of Borchert
(1948) and also his optical rotation data, publishing similar interpretations
N. Morin-Crini et al.
rings, i.e., five and six, respectively, using a cryoscopic method were incorrect. The
correct values were determined by French using both X-ray diffraction and crystal
density measurements.
Between 1942 and 1965, French also contributed greatly to the molecular structural knowledge of the Schardinger dextrins, or, as he preferred to call them,
cycloamyloses (Caesar 1968; Szejtli 1998; Crini 2014). Very quickly, French
became a pioneer in the understanding of their structure, publishing an impressive
number of results on cycloamyloses which are still used as references today (French
and Rundle 1942; Rundle and French 1943; Bates et al. 1943; French et al. 1948,
1949a, b, 1950a, b, 1954; French and McIntire 1950; Norberg and French 1950;
French 1957a, b, 1960, 1962; Bailey and French 1957; Thoma and French 1958,
1959, 1960, 1961; James et al. 1959; Thoma et al. 1959; Whelan et al. 1960; Pulley
and French 1961; Robyt and French 1964; French and Abdullah 1965; French et al.
1963, 1965). French’s first work concerned the molecular weights of the Schardinger
dextrins, considered as cyclic molecules in agreement with the previous results published by Freudenberg (Freudenberg and Meyer-Delius 1938; Freudenberg et al.
1938). French and Rundle (1942), using the X-ray diffraction technique and crystal
density measurements, determined the molecular weights of α-dextrin and β-dextrins
and discovered the exact number of glucose units per dextrin, i.e., six and seven,
respectively, in disagreement with the results published by Freudenberg and Jacobi
(1935). French and Rundle demonstrated that molecular weights were integral multiples of the value 162.1 for a glucose residue. They concluded that the X-ray diffraction technique was better suited to the determination of the molecular weights
of high molecular weight crystalline substances since impurities, such as solvent of
crystallization and inorganic ash, were of minor importance (French and Rundle
1942). In this paper, French also suggested that Schardinger dextrins were cyclic
“macromolecules,” formed from starch polysaccharide (French and Rundle 1942).
They were non-reducing “D-glucopyranosyl polymers” containing 6, 7, or 8 units
linked by α-D-(1→4) bonds, in agreement with the results published by Karrer
(1923) and Miekeley (1932). In each cycloamylose “macromolecule,” the D-glucose
units were in the C1 conformation. Schardinger dextrins were then regarded as cylinders (French and Rundle 1942). However, Freudenberg did not agree with this
point of view (Freudenberg 1943).
French pointed out three interesting features: (1) as a consequence of the C-1
conformation of the glucopyranose units, all the secondary hydroxyl groups were
located on one side of the cylinder, whereas all the primary hydroxyl groups were
located on the opposite side of the cylinder; (2) the interior of the cylinder consisted
only of a ring of C-H groups, a ring of glucosidic oxygens, and another ring of C-H
groups; and (3) the interior of the cavity was relatively apolar compared to water
(French and Rundle 1942; Rundle and French 1943; Bates et al. 1943; French et al.
1948, 1949a, b). Freudenberg claimed again that all the structural and conformational conclusions of French were ambiguous due to “the use of products that were
not pure” (Freudenberg et al. 1947a, b). One year later, Freudenberg and Cramer
concurred with French’s results, after studying the X-ray measurements of Borchert
(1948) and also his optical rotation data, publishing similar interpretations
N. Morin-Crini et al.