Publisher Summary This chapter assesses the progress of one research group that found a new general approach for lengthening the carbon chain or inserting a branched chain into the carbon chain of sugars. Brief mention is made of the use of the new, unusual sugars in the synthesis. The approach utilized by this research group involves the use of transition-metal carbonyls as catalysts for inserting carbon monoxide into the carbon chain of the carbohydrate. In all cases, there are, apart from the catalyst, three components in the system: the substrate, carbon monoxide, and hydrogen. The substrates used are unsaturated carbohydrates containing a carbon–carbon double bond, anhydro-sugars having an ethylene oxide ring, and carbohydrates containing a halogen atom attached to a carbon atom of the carbon chain.