A-Gentiobiose

Octa-Ac Octa-O-acetyl-a-gentiobiose C28H38O19 678.597 Mp 188-189°. [a]g +52.3 (CHCI3). 

Gentiobiose, a carbohydrate found in saffron, contains two glucose molecules linked by a /3-1,6-glycosidic bond. Draw the Haworth structure for a-gentiobiose. (18.1, 18.2)... 

Some of the original work in the carbohydrate area in particular reveals extensive protection of carbonyl and hydroxyl groups. For example, a cyclic diacetonide of glucose was selectively cleaved to the monoacetonide. A summary describes the selective protection of primary and secondary hydroxyl groups in a synthesis of gentiobiose, carried out in the 1870s, as triphenylmethyl ethers. 

On either side of the crocetin molecule is a disaccharide molecule called beta-gentiobiose, and the result is the molecule that gives saffron its yellow color. 

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