164
the main individual bands (Casu and Reggiani 1964). The IR spectra were taken
with a Perkin-Elmer model 125 spectrophotometer. In this paper, he suggested for
the first time a common shape of the glucopyranose rings, in the chair C-1, in all the
starch derivatives studied, and the presence of hydrogen bonds between the hydroxyl
groups (Crini 2014). The same year, Professor Casu also published hydroxyl proton
resonances of sugars in water and dimethyl sulfoxide solutions in order to characterize the structural factors which affected ring vibrations in infrared data and to clarify the significance of their shifts ongoing from cyclic to linear structures (Casu
1964; Casu et al. 1964). Later, he detailed NMR spectra and conformation of glucose and some related carbohydrates in the same conditions (Casu et al. 1965b,
1966, 1967, 1968b).
In 1965, an IR spectrophotometric procedure was developed for determining
water in carbohydrates (Casu et al. 1965a). The method was based on the measurement of the intensity of 1655 cm
−1
band of water in a solution of the hydrated sugar
in dimethyl sulfoxide. This method was particularly interesting when unsubstituted
carbohydrates contained crystallized water. The average percent difference between
the results obtained by the IR versus the usual oven-drying method was find to be
about ±1%. One year later, his results clearly demonstrated that the amylose macromolecule had a flexible structure, with a helical pattern, which could take various
conformations through rotation of the monomeric blocks around the glucosidic
linkages (Casu and Reggiani 1966). Both IR and NMR spectra showed that the
C1-H bond was equatorial and C1-O axial, also confirming the C-1 chair conformation of the glucopyranose units (Casu and Reggiani 1964, 1966). Professor Casu
also showed the existence of intermolecular hydrogen bonds contributing to the
stabilization of the helical structures. At that time, these works were acknowledged
to have made an important contribution to this topic (Crini and Torri 2017; Crini
et al. 2018). Professor Casu obtained similar results when studying the native
cycloamylose molecules, particularly cyclohexaamylose or α-cyclodextrin, with the
first IR and
1
H-NMR spectroscopic studies (Casu and Reggiani 1964, 1966). The
cycloamylose samples were prepared by Professor French.
3.3.2 Professor Casu and Cyclodextrins
Professor Casu was also on the list of prestigious researchers, such as Professors
Dexter French, Friedrich Cramer, Myron Lee bender, József Szejtli, and Wolfram
Saenger, who contributed in the 1960–1970s to the development of cyclodextrins
(Crini 2014). Few researchers at that time believed in the potential that these new
molecules had (Szejtli 1982, 1988; Crini 2014; Crini et al. 2018).
Professor Casu showed that IR and
1
H-NMR spectroscopy were powerful methods to study the conformations of not only amylose and linear dextrins but also
cyclodextrins. In the middle of the 1960s, he investigated for the first time the NMR
spectra of cyclodextrins (Casu 1964, 1968a, b), and his conclusions greatly advanced
the understanding of the structure and chemistry of cyclodextrins and their
G. Torri et al.
the main individual bands (Casu and Reggiani 1964). The IR spectra were taken
with a Perkin-Elmer model 125 spectrophotometer. In this paper, he suggested for
the first time a common shape of the glucopyranose rings, in the chair C-1, in all the
starch derivatives studied, and the presence of hydrogen bonds between the hydroxyl
groups (Crini 2014). The same year, Professor Casu also published hydroxyl proton
resonances of sugars in water and dimethyl sulfoxide solutions in order to characterize the structural factors which affected ring vibrations in infrared data and to clarify the significance of their shifts ongoing from cyclic to linear structures (Casu
1964; Casu et al. 1964). Later, he detailed NMR spectra and conformation of glucose and some related carbohydrates in the same conditions (Casu et al. 1965b,
1966, 1967, 1968b).
In 1965, an IR spectrophotometric procedure was developed for determining
water in carbohydrates (Casu et al. 1965a). The method was based on the measurement of the intensity of 1655 cm
−1
band of water in a solution of the hydrated sugar
in dimethyl sulfoxide. This method was particularly interesting when unsubstituted
carbohydrates contained crystallized water. The average percent difference between
the results obtained by the IR versus the usual oven-drying method was find to be
about ±1%. One year later, his results clearly demonstrated that the amylose macromolecule had a flexible structure, with a helical pattern, which could take various
conformations through rotation of the monomeric blocks around the glucosidic
linkages (Casu and Reggiani 1966). Both IR and NMR spectra showed that the
C1-H bond was equatorial and C1-O axial, also confirming the C-1 chair conformation of the glucopyranose units (Casu and Reggiani 1964, 1966). Professor Casu
also showed the existence of intermolecular hydrogen bonds contributing to the
stabilization of the helical structures. At that time, these works were acknowledged
to have made an important contribution to this topic (Crini and Torri 2017; Crini
et al. 2018). Professor Casu obtained similar results when studying the native
cycloamylose molecules, particularly cyclohexaamylose or α-cyclodextrin, with the
first IR and
1
H-NMR spectroscopic studies (Casu and Reggiani 1964, 1966). The
cycloamylose samples were prepared by Professor French.
3.3.2 Professor Casu and Cyclodextrins
Professor Casu was also on the list of prestigious researchers, such as Professors
Dexter French, Friedrich Cramer, Myron Lee bender, József Szejtli, and Wolfram
Saenger, who contributed in the 1960–1970s to the development of cyclodextrins
(Crini 2014). Few researchers at that time believed in the potential that these new
molecules had (Szejtli 1982, 1988; Crini 2014; Crini et al. 2018).
Professor Casu showed that IR and
1
H-NMR spectroscopy were powerful methods to study the conformations of not only amylose and linear dextrins but also
cyclodextrins. In the middle of the 1960s, he investigated for the first time the NMR
spectra of cyclodextrins (Casu 1964, 1968a, b), and his conclusions greatly advanced
the understanding of the structure and chemistry of cyclodextrins and their
G. Torri et al.