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In the typical introductory organic chemistry course, students work questions out of a textbook for which a solutions manual is available. They struggle with a question for a few minutes, look up the answer, and then believe they know how to answer the question. It isn't until exam time that they realize that knowing an answer to a question and knowing how to answer a question are two entirely different propositions.Computer programs that tell a student that a response is incorrect without supplying the correct answer are likely to be more effective teaching tools. Many Web-based chemistry homework programs exist (1-5), but most require text-based, numeric, or multiple-choice answers. In organic chemistry, however, answers are usually structural drawings. The only program we are aware of that allows a student to draw a chemical structure in response to a question is OWL 1 (1), as implemented at the Web site for McMurry's Organic Chemistry ( 6).The electronic program for organic chemistry homework (EPOCH) is a Web-based application designed specifically for instructors and students of introductory organic chemistry. EPOCH prompts students to construct a structural response to a posed question with a graphical structure-drawing interface. EPOCH offers feedback that explains why a response is correct or incorrect, guiding students to the correct answer. The author of a question decides what characteristics of a student's response should elicit what feedback from EPOCH: for example, the presence of a particular atom or functional group ("Br is a leaving group; it should not be present in your product."), the absence of a certain skeleton ("No C-C bonds should be formed or broken in this reaction."), or the configuration of a stereocenter ("What is the stereochemical result of an S N 2 reaction?"). EPOCH never reveals the correct answer; students must attack the question repeatedly until they answer it correctly. EPOCH's designers understand that students learn far more from struggling to answer a question correctly than from being told the correct answer. By contrast, most Web-based homework programs do not provide feedback for wrong answers, and most allow the student to give up before answering the question correctly (1,3,4). To our knowledge, the only program that provides feedback to students that is based on their free responses (not multiple-choice responses) is the Quantum Tutor (2).

[reaction: see text] The three-carbon alpha,alpha'-annulation of a sterically hindered cyclic beta-keto ester can be achieved by alkynylation with 3,3-diethoxypropyne, syn reduction of the alkyne with Co(2)(CO)(8) and Et(3)SiH, and an intramolecular aldol reaction. The method is potentially useful for the synthesis of nemorosone, hyperforin, and other polycyclic polyprenylated acylphloroglucinols.

The purpose of this work was to synthesize a series of symmetrical analogs (CA2-CA7) of curcumin and determine their efficacy as antioxidant and anticancer agents in vitro. The six analogs were successfully synthesized and characterized, one of which, CA6, had not been previously reported in the literature. With the exception of CA2, the analogs had lower predicted aqueous solubilities and higher partition coefficients than curcumin. Two analogs, CA2 and CA3, had lower potencies as anticancer agents compared with curcumin, while CA6 had a slightly higher IC50 value. Two different trends in the antioxidant capabilities of curcumin and its analogs were determined when assessed in vitro or in cell culture. The in vitro DPPH assay clearly showed curcumin as the strongest antioxidant as compared with the analogs when tested at the same concentration or at their IC50 value. The cell culture-based reactive oxygen species/reactive nitrogen species assay indicated that CA3 and CA6 were equal to curcumin in their free radical scavenging ability at the same concentration, but when curcumin and its analogs were tested at their respective IC50 values, CA4 and CA5 showed excellent antioxidant capacities. These results indicate that in cell culture, the ability of these analogs to produce antioxidant effects may be tied to their downstream effects.