Woodward dramatically advanced the developing art of organic synthesis in the mid-20th century, accomplishing a series of total syntheses of highly complex natural products. Total synthesis means constructing a natural molecule entirely from inexpensive feedstocks such as petroleum through many reaction steps. He introduced the idea of breaking a target molecule into pieces and planning backward – an approach now called retrosynthesis – and achieved remarkable yields by skillfully using protecting groups and functional-group interconversions. As a result, he synthesized molecules once deemed impossible, including cholesterol, strychnine and vitamin B12, greatly expanding the scope of pharmaceutical research. He also established rigorous control of stereochemistry, enabling progress toward optically pure drugs. His work influenced not only mass production of medicines but also the conceptual foundations of molecular models and modern reaction-planning software, directly shaping contemporary drug discovery.

Woodward’s research was revolutionary both in route-design philosophy and in the control of reaction selectivity. He dissected target skeletons and identified specific functional groups as ‘key handles,’ then assembled them stepwise. In the quinine synthesis, for instance, he pre-constructed the quinamidine and quinuclidine fragments, later coupling them via asymmetric alkylation and Michael addition. For vitamin B12, he introduced sequential ring closures and photochemical steps, directing what was then the largest international collaboration in organic chemistry. The accumulated experience codified the very ‘language’ of synthesis: protecting-group logic, stepwise yield management and fine-tuning of reaction conditions. He also proposed the Woodward-Hoffmann rules, providing a theoretical explanation of pericyclic reaction symmetry and enabling predictive orbital-interaction reasoning. Modern computer-assisted synthesis planning (CASP) and catalytic asymmetric synthesis trace directly back to these achievements.

Woodward’s total-synthesis achievements demonstrate a systematic methodology integrating molecular design with reaction engineering. His approach matured into retrosynthetic analysis that combined electronic considerations and stereochemical requirements, foreshadowing today’s positional disconnection methods. In the quinine synthesis he employed a 6-methoxyquinazoline derivative as a key intermediate and used a Smiles rearrangement to forge the C9–C10 bond. The vitamin B12 project adopted covalent segment coupling, building the corrin-porphyrin framework through photochemical A-ring fusion and a benzoin condensation while maintaining yields in the 5×10−5 % range over more than 90 steps. Selectivity control involved low-temperature lithiation, crown-ether auxiliaries and precise pH modulation, pioneering multi-stage process management. Though not part of the 1965 award, the orbital-symmetry rules he later formulated with Hoffmann offered a groundbreaking theory predicting allowed and forbidden pericyclic reactions based on π-transition-state symmetry, finding applications even in modern organic electronic material design. His body of work also serves as a benchmark for synthesis-route search algorithms, providing training data for contemporary machine-learning models that design macromolecular therapeutics.