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Remember when…︁? This Essay describes the collaboration between Stewart Rubenstein and David and Sally Evans to develop the chemical graphics program ChemDraw, which was introduced in 1986. Now, three decades later, this software has become the dominant vehicle for drawing chemical structures in the organic chemistry community.

Wie alles anfing: Dieser Essay beschreibt die gemeinsamen Anstrengungen von Stewart Rubenstein und David und Sally Evans bei der Entwicklung des Zeichenprogramms ChemDraw, das 1986 eingeführt wurde. Heute, drei Jahrzehnte später, ist diese Software das am häufigsten benutzte Werkzeug für chemische Strukturzeichnungen in der organischen Chemie.

ALICE is a multi-media framework for ICALI programs that is being developed at Carnegie Mellon University. It is not a single instructional program, but rather a set of tools for building a number of different types of ICALI programs in any language. The central components of ALICE are (1) a set of Natural Language Processing (NLP) tools for syntactic error detection, morphological analysis, and generation of morphological paradigms, (2) a set of on-line text, video, and audio corpora that serve as sources of realistic, in-context examples, and (3) an authoring language that allows teachers to configure the NLP tools and excerpts from the corpora into ICALI programs. This paper describes the NLP components of ALICE and the role of excerpts from corpora in treating student errors. workstation, authoring system, automated error detection, CLARIT system, cognitive research, computational linguistics, detectable rule-governed errors, error analysis feedback, error detection using NLP, foreign-language video-disk, GENKIT sentence generator, ICALI program, indexed text, inflectional paradigm generator, intelligent tutoring system (ITS), language acquisition, language corpus, left-associative morphology program, lexicon, LISP program, machine-readable knowledge base, morphological analysis, morphological generation program, natural-language parsing, natural-language processing (NLP), NLP helping students, on-line dictionary, on-line reference capability, on-line text, pattern matcher, Spanish writing assistant, speech-act situations, student interface, text base, Tomita parser, unification based grammar rules.

The convergent synthesis of the polycyclic alkaloid (-)-nakadomarin A (1) is reported. The synthesis plan identified macrocyclic lactam 4 as one of the important synthons (eight steps). The other synthon (five steps) was bicyclo[6.3.0] lactam 5 containing a single stereocenter that controlled all of the subsequent stereochemistry during the assembly process. A silyl triflate-promoted cascade of 4 and 5 was used to assemble the bulk of the alkaloid skeleton with the exception of the C5-C6 bond. The nakadomarin synthesis was then completed in one additional step.

The 1990 amendments to the Clean Air Act created a trading program in sulfur dioxide (SO2) emissions that has served as the seminal example of how an emissions trading program could be designed. Yet despite its success, the trading program was essentially brought to an end by a series of regulatory and judicial actions. We begin with a brief discussion of the theoretical and historical antecedents to the SO2 trading program. We then describe the events that led to the program's effective end in 2011. We argue that the SO2 trading program had two key vulnerabilities: SO2 emissions cause multiple environmental impacts, some with local consequences, and internal conflicts within the Clean Air Act. Because of these vulnerabilities, in the end, the program was unsustainable. We close with a discussion of the lessons that can be drawn from this history for future emissions trading programs.

To examine whether adherence to a Mediterranean-based dietary pattern is predictive of depressive symptoms among older adults.

Two transannular (TA) aldol reactions were used to assemble the tricyclic carbon skeleton found in the tigliane and daphnane classes of diterpene natural products.

A new approach to the tetracycline core structure is presented. The pivotal intermediate is identified as macrocycle III. The two interior bonds (C4a-C12a and C5a-C11a) are to be constructed through sequential transannular Michael additions (III-II) and compression-promoted transannular isoxazole alkylations from intermediate II.

A full account of our total synthesis of the galbulimima alkaloids GB 13 and himgaline is provided. Using a strategy adapted from the proposed biosynthesis of the GB alkaloid family, a linear precursor underwent successive intramolecular Diels-Alder, Michael, and imine aldol cyclizations to form the polycyclic alkaloid core. We now show that modification of this strategy can also deliver an advanced intermediate en route to the related alkaloid himandridine. The success of the key imine aldol cyclization is acutely sensitive to substrate structure and solvent, including a case in which cyclization was spontaneous in protic solvents. A detailed computational investigation of the course of the reaction closely correlates with, and suggests a rationale for, the observed patterns of imine aldol reactivity.

We present a general model for understanding the stereochemical course of intramolecular Michael reactions. We show that the addition of β-ketoester enolates to α,β-unsaturated esters and imides bearing adjacent stereocenters (X, Y = H, Me, OR) leads to high levels of asymmetric induction. Reinforcing and nonreinforcing stereochemical relationships are evaluated from the syn and anti reactant diastereomers. On the basis of synthetic, spectroscopic, and computational studies, we propose that the outcomes of these reactions can be rationalized by a dipole-minimized chair transition-state model.

The use of cyclic alpha,beta-unsaturated iminium-ion dienophiles is documented in two highly diastereoselective Diels-Alder (DA) reactions. The dienophilic counterion was found to have a significant effect on reactivity.