Notes- A New Synthesis of D-Rhamnose (6-deoxy-D-mannose)

Organic chemistry

“…49 Nevertheless, the recent measurements of 13C-chemical shifts are sufficient to show that this may be the most sensitive way of probing the n-electron densities in isolated aromatic molecules. As expected, the range of chemical shifts in alternant aromatic hydrocarbons is ~Iight,~O but a much greater variation occurs with azulene 4 7 9 50 and this has led to a set of n-electron densities in good agreement with recent calculations.51, 52 In monosubstituted benzenes the 13C-chemical shifts are small at the rnetaposition, and generally as expected at the para-positi~n;~~, 53 at the orthoposition some apparent anomalies occur; thus the n-electron density at the ortho-position in nitrobenzene appears to be greater than 53 The most recent calculations suggest that the n-electron density in this position should be a little less than unity. 54 Related studies of proton chemical shifts have concerned a~ulene,~7 the pyridine ring and trisubstituted benzenes.56 I n a general review of o-values, Taft 57 has discussed the variation of the lgF-chemical shifts with the inductive (oI) and resonance (a,) parameters of other substituents.…”

“…Contrary to an earlier report, benzene, on irradiation with y-rays from a cobalt-60 source, apparently does not yield optically active decomposition products. 50 Brewster's molecular-rotat'ion method, referred to above, should permit the semi-empirical prediction of both sign and magnitude of rotation, and hence afford an excellent general method for determination of absolute co6guration. It has been applied t o a variety of compounds-cyclopro-~a n e s , ~1 norbornanes,52 quercitols,5~ steroids 54-with overall varying success ; obviously some further development is required.…”

“…Hofmann degradation does, however, result in aromatisation. The mechanism suggested for the haemanthamine ester-isohzmanthamine change is given in (50), the nature of R depending on the mode of hydrolysis-aqueous sodium hydrogen carbonate gives a product with R = OH and methanolic potassium hydroxide gives one with R = OMe. O-Methylation of isohsmanthamine gives the alkaloid manthine.…”

Synthesis of Some Disaccharides Containing Rhamnose as the Nonreducing Unit

“…So an attempt was made to synthesize some 1--> 2 linked disaccharides containing D-or L-rhamnose as the nonreducing unit to develop our study, We describe in the present paper the synthesis of hepta-O-acetyl-2-0-rx-D-rhamnopyranosyl-rx-D-galactopyranose (I), hepta-O-acetyl-2-0-rx-L-rhamnopyranosyl-p-D-mannopyranose (II) and hepta-O-acetyl-2-0-rx-L-rhamnopyranosyl-rx-D-galactopyranose (III). DRhamnose (IV) has already been synthesized by Haskins et 01.,2) Zorbach et 01., 3) and Bock et 01. 4) We synthesized the acetate (IV') of IV in an alternative manner.…”

Food Industrial Production of Monosaccharides Using Microbial, Enzymatic, and Chemical Methods

“…l-Rhamnose is a naturally occurring deoxy sugar that occurs as 6-deoxy-l-mannose [33]. As a method for obtaining l-rhamnose for cosmetic ingredients or food additives, glycoside contained in the pericarp, bark, or flowers of Rutin or Citrus is isolated, and the fermented product is then concentrated, separated, hydrolyzed, and separated again to obtain l-rhamnose.…”