11.13.6 The Ruff Degradation

Aldose chain is shortened by oxidizing the aldehyde to –COOH, then decarboxylation. In the Ruff degradation, the calcium salt of an aldonic acid is oxidized with hydrogen peroxide. Ferric ion catalyzes the oxidation reaction, which cleaves the bond between C-1 and C-2, forming an aldehyde. The calcium salt of the aldonic acid prepared from oxidation of an aldose with an aqueous solution of bromine and then adding calcium hydroxide to the reaction mixture (Scheme 10).

Scheme 10

11.13.7 The Kiliani–Fischer Synthesis

An aldose carbon chain can be increased by one carbon in a Kiliani–Fischer synthesis (Scheme 11). It is the opposite of Ruff Degradation reaction. This synthesis leads to formation of a pair of C-2 epimers.

Scheme 11

D-Erythrose gives the corresponding chain lengthened products D-ribose and D-arabinose (Scheme 12).

Scheme 12