This document describes biochemical pathways for producing a difunctional product having an odd number of carbon atoms in vitro or in a recombinant host, or salts or derivatives thereof, by forming two terminal functional groups selected from carboxyl, amine, formyl, and hydroxyl groups in an aliphatic carbon chain backbone having an odd number of carbon atoms synthesized from (i) acetyl-CoA and propanedioyl-CoA via one or more cycles of methyl ester shielded carbon chain elongation or (ii) propanedioyl-[acp] via one or more cycles of methyl ester shielded carbon chain elongation. The biochemical pathways and metabolic engineering and cultivation strategies described herein rely on enzymes or homologs accepting methyl ester shielded aliphatic carbon chain backbones and maintaining the methyl ester shield for at least one further enzymatic step following one or more cycles of methyl ester shielded carbon chain elongation.