{"knowledge_schema": {"broad_category": "Chemistry \u2192 Organic Chemistry \u2192 Reaction Mechanisms", "refinement": "This problem involves understanding the stereochemistry and reactivity of organic compounds in reduction reactions.", "specific_scope": "The focus is on identifying the correct starting materials for two separate reactions that yield specific stereoisomers of a product after reduction with different agents.", "goal": "Determine the appropriate starting materials (A and B) that lead to the desired products with the specified stereochemistry."}, "summary": "This problem is rooted in organic chemistry, specifically in the area of reaction mechanisms and stereochemistry. It requires identifying the correct starting materials for two reduction reactions that yield specific stereoisomers of a compound. The goal is to select the appropriate candidates from the provided options that will lead to the desired products after treatment with different reducing agents. The correct answer indicates that both starting materials A and B are the same compound, which is (S)-3-ethyl-5-isobutoxy-5-oxopentanoic acid."}