bluuebunny/crossref_metadata_2025 huggingface dataset:
General procedures: starting materials and reaction guidelines
Authors: Taylor Richard J K , Casy Guy
Published: November 2023

This chapter contains information concerning the starting materials required for organocopper reactions (commercial availability, preparative procedures, purification, etc.), together with a discussion of the apparatus and techniques commonly employed when carrying out such reactions. A number of copper salts and their complexes have been employed for the preparation of cuprate reagents, copper(I) iodide being the most popular. It has been shown in comparison experiments, however, that CuCN and CuBr-SMe2 are equally useful, if not better, organocuprate precursors. Copper(II) salts used in copper-catalysed Grignard reactions are reduced to the active copper(I) species by excess Grignard reagent. Table 2.1 lists copper-containing starting materials that have been employed in organocopper reactions and includes brief notes on suppliers, preparation/purification procedures, and synthetic utility.
Preparation of organocopper reagents using active copper
Authors: Rieke R D , Klein W R
Published: November 2023

Organocopper reagents have intensively been used in synthetic chemistry. The vast majority of organocopper reagents are prepared by a transmetallation reaction involving an organometallic reagent and a copper(I) salt. A variety of organometallic reagents, derived from metals more electropositive than copper, have been utilized in the preparation of organocopper reagents. The most common organometallic precursors have been organomagnesium and organolithium reagents. This approach severely limits the functionality that may be incorporated into the organocopper reagent. The use of traditional lithium or Grignard precursors can be circumvented by using a highly reactive zero-valent copper which directly undergoes oxidative addition to organic halides.
Preparation of highly functionalized reagents
Authors: Knochel Paul , Rozema Michael J , Tucker Charles E
Published: November 2023

Many organocopper reagents are prepared from the corresponding magnesium or lithium organometallics. Unfortunately, this approach precludes the presence of most functional groups in these copper reagents, since they would not be tolerated in the starting magnesium or lithium reagent. However, functionalized copper reagents of the type FG—RCu(CN)ZnX can be prepared starting from organozincs (RZnX or R2Zn) by performing a trans-metallation using the soluble copper salt CuCN•2LiCl (eqn 1). Since organozincs bearing a wide range of functionalities such as a cyanide (Protocol 1), an ester (Protocol 2), a ketone, an enone (Protocol 4), an amine, a terminal alkyne (Protocol 3), a phosphonate, a halide, sulfur functionalities (SCOR, SR, SOR, SO2R), or a trialkoxysilyl group [Si(OR)3] can be easily prepared, this method offers a general access to polyfunctional copper reagents.
Me3SiCl-accelerated conjugate addition reactions of organocopper reagents
Authors: Nakamura Eiichi
Published: November 2023

Conjugate addition to α,β-unsaturated carbonyl compounds represents an archetypical reaction of organocopper reagents (eqn 1). Various reagents including the classical Grignard-based catalytic copper reagent, the Gilman reagent (R2CuLi), and the ‘RCu•BF3’ reagent have been developed to improve the efficiency of the process by enhancing the reactivities of the reagents and by suppressing side-reactions such as 1,2-addition. Because of the paramount importance of the conjugate addition in organic synthesis, research efforts continue to make the reaction more versatile and more reliable. This chapter describes the Me3SiCl-accelerated reactions of organocopper reagents—a methodology which has proven its great synthetic utility in the past several years.
Synthetic applications of silylcuprates and stannylcuprates
Authors: Fleming Ian
Published: November 2023

Silylcopper and stannylcopper reagents and the corresponding cuprates react with many of the same substrates (Scheme 12.1) as their carbon-based counterparts. The products carry on their carbon framework a silyl or stannyl group, with which many transformations can be carried out, replacing these functional groups with carbon groups or with other functional groups. In addition, silylcuprates and stannylcuprates react with unactivated allenes to give vinyl or allyl derivatives depending upon the structure of the allene. In general, silylcopper and stannylcopper reagents and the corresponding cuprates appear to be thermodynamically more stable in THF solution than their carbon-based counterparts, allowing them to be treated with their substrates at temperatures of 0°C and above over several hours if necessary, although it rarely is, because they appear to be simultaneously kinetically more reactive than the carbon-based reagents, reacting with substrates such as allenes and α,β-unsaturated esters that carbon-based cuprates do not react with in the normal course of events.
Powder diffraction: data collection, refinement, results
Authors: Baerlocher Ch.
Published: November 2023

The principle handicap of the powder method is the fact that the three dimensional diffraction data are projected onto a one-dimensional array. The associated loss of information has given the powder method a bad reputation in many quarters of the natural sciences. Powder data is viewed as something to be avoided. However, this picture has changed in recent years. It is, of course, still true that powder data are, for the most part, inferior to single crystal data, but the progress achieved in both instrumentation and data analysis have led to a growing awareness of the potential of the powder method, and to an increasing recognition of the quality of the results. This success is due, to a significant extent, to the Rietveld method. In this method the problem of overlapping reflections is circumvented by fitting the whole diffraction pattern step by step.
The Solution of Large Small-Molecule Structures and Small Macromolecules
Authors: Sheldrick George M
Published: November 2023

abstract

As pointed out in a recent editorial inScience (Moffat, 1992), the phase problem is probably most difficult to solve for ‘mid-sized’ molecules of about 200-500 non-hydrogen atoms. Direct methods rarely fail on structures of less than I 00 atoms and are often successful up to about 200 atoms; the largest unknown structure to be solved purely by direct methods is probably gramicidin-A, with 334 unique atoms (Langs, 1988). Classically, most proteins have been solved by the preparation of heavy-atom derivatives, but the introduction of such atoms distorts smaller molecules severely, leading to lack of isomorphism, an essential requirement of the MIR method. Molecular replacement - using a fragment of a related structure as a search probe, usually in Patterson space - is applicable to both small molecules and macromolecules, but many mid-sized structures of biological interest possess more conformational flexibility than this approach can tolerate.
Charge density determination by X-ray diffraction
Authors: Koritsánszky Tibor
Published: November 2023

Many aspects of the chemical bond and molecular structure are directly related to the electron density which can be determined by advanced theoretical and experimental techniques. Each method has its own advantages and limitations and their applicability is subject to different conditions. The molecular electron distribution continuously rearranges itself due to the motion of the nuclei. Under certain assumptions the averaged dynamic distribution is deducible from the static density of the equilibrium structure. The X-ray is scattered by the electrons and the diffracted intensity is related to the electron distribution. The simplest theory applied to interpret the measurement states that the time averaged scattering is dominated by the scattering from the thermally averaged distribution. The observed data are limited and their interpretation must involve modelling.
User interface management systems (UIMS) for crystallography
Authors: Bourne Philip E
Published: November 2023

Advances in hardware and software technology are changing the way crystallographers interact with the computer. Bit-mapped graphics displays as found on workstations, X-terminals, and personal computers, when combined with Graphical User Interface (GUI) software, provide a more sophisticated interface beyond that available using a character-based terminal. To date, most crystallographers use only the standard screen objects supplied with the GUI. These objects include terminal emulation windows for multi-tasking and desktop accessories such as calculators, notepads, and user executives. (User executive is one of several terms for screen objects that simplify interaction with the base operating system.)
New approaches to crystallographic software
Authors: Murray-Rust Peter , Zelinka Jan
Published: November 2023

The problem of developing and maintaining software systems is enormous and has reached a crisis point in many disciplines - crystallography is no exception! Most disciplines have code developed over many years, by many authors with varying degrees of coordination. When people on a project move away, or the code has to be ported to a new machine it is often simplest (though very costly) to rewrite the system from scratch! Crystallographic software development has often been imaginative and effective. Among our community’s contributions have been free-format input, graphical output, high-performance graphical techniques and databases. The collaboration in the community is also a very important factor, leading to program libraries, and integration of many different authors’ work in packages. This philosophy puts crystallography in an excellent position to take advantage of the new software techniques that are becoming available.
Introduction and general methods
Authors: Williams Jonathan M J
Published: November 2023

This book is designed to provide advice on the synthesis of alkenes using some of the more common methods currently used by organic chemists. It is not possible to provide a detailed account of every method of alkene preparation that has ever been employed. However, discussion sections and literature references should enable the more adventurous chemists to devise their own practical experiments for the synthesis of alkenes.
Chemical transformations
Authors: Isaacs Neil S
Published: November 2023

Only a brief outline of the effects of pressure on rates and equilibria is given here since the subject is amply documented elsewhere.1-4 It has long been appreciated that the position of a chemical equilibrium may be shifted by the application of external pressure in reactions in both the liquid and the gaseous phase. This shift in equilibrium favours the direction of the reaction which results in the smaller volume; this is an application of the Le Chatelier’s principle. In gas-phase reactions the term volume denotes the total volume of the system; in dilute solutions the term volume denotes the algebraic sum of the partial molar volumes of the individual reagents and products.
Cryptands
Authors: Dietrich Bernard
Published: November 2023

The cryptands were first prepared in 1969 and form a series of well-defined complexes (cryptates) with alkali and alkaline-earth cations. In this chapter the synthesis of the first cryptand, 8, a macrobicyclic ligand, will be described. The schematic representation (Fig. 5.1) shows that one deals with a multi-step synthesis. The major drawback of this approach is the rather large number of synthetic steps, but the route offers the advantage of being able to construct unsymmetrical compounds (A ≠ B ≠ C).
The Natural Selection of the Chemical Elements
Authors: Williams R J P , Da Silva J J R Frausto
Published: November 2023

The central thesis of The Natural Selection of the Chemical Elements is that the inanimate environment and living organisms are intimately connected, and that the evolution of both has been interactive and interdependent: the environment and life developed together. The authors show that this can be explained in terms of the properties of the chemical elements and their compounds, especially as compounds have developed with time. The first part of the book discusses the physical and chemical balance between ordered and disordered systems and then analyses organisation in both the animate and inanimate worlds. Appropriate thermodynamic and kinetic principles are given to support this analysis. The application of these principles to the development of both inorganic (geographical) and organic chemical systems is then described, providing a basis for understanding the evolution of life in terms of the interaction of both types of chemistry within ever more complex organisations. The book concludes by examining the long-term consequences of man's selection and manipulation of chemicals for his own purposes which may have consequences for the long-term future of life from changes in the environment - not only due to bulk but also to trace element alterations.
Limited phases, fields and compartments
Authors: Williams R J P , Da Silva J J R Frausto
Published: November 2023

In this chapter we wish to approach more closely the nature of the observable systems around us be removing in steps the assumptions that were employed in our discussions of equilibria in Chapters 4 and 5. These assumptions were that: (1) the phases had no surfaces, but as soon as we limit the total amount of a system, which we must do now, surfaces become important-the real world around us is constrained by divisions of space with surfaces; (2) there were no fields acting on a phase; however, as soon as we consider contact or a region between phases, that is, phases with surfaces, we must consider fields gravitational, mechanical and electrical; (3) there was equilibrium transfer of material and energy between phases, but in the real world there are boundaries between compartments containing phases that prevent at least some transfer; for example, the presence of semipermeable membranes is the basis of living constructs. Clearly, these three additional features, surfaces fields, and transfer of matter or energy, limit the applicability of the previous discussion of both bulk phases (Chapter 4) and of dilute solutions in isolated phases (Chapter 5). We must, therefore, look first at the effects of limited total amounts of material and the presence of fields on the variance of systems, as predicted by an extended form of the phase rule. We need then to describe the effects of barriers to transfer between compartments, that is, removal of the transfer equilibria for both bulk and dilute components. We shall find that, when we add all these factors together, substances around us cannot but be extremely diversified and far from even local equilibrium. However, as we explained in Chapter 3, it is only by reference to equilibrium that we can gain the basic understanding necessary for the appreciation of out-of-equilibrium systems and the directions of change. One of the major considerations in Chapters 4 and 5 was to establish the limits of variance of systems, that is, the number of degrees of freedom, from the use of equilibrium considerations in the phase rule. We, therefore, start the discussion in this chapter with a brief summary of the position we established in those chapters.
Transition metal-promoted oxidations
Authors: Woodward Simon
Published: November 2023

Few other areas of modern synthetic organic chemistry offer the diversity shown by homogeneous catalytic oxidation reactions. Practically all the transition metals have complexes showing oxidation activity; widely disparate mechanisms of action are standard.
Organoiron chemistry 1: ferrocene and dienyl iron tricarbonyl cation chemistry
Authors: Richards Christopher J
Published: November 2023

This chapter deals with two differing applications of organoiron chemistry to organic synthesis. In the first section the chemistry of ferrocene is examined, in particular the reactions required for the construction of ferrocene-based ligands, which have found wide usage in asymmetric catalysis. In contrast, the cationic dienyl iron tricarbonyl complexes studied in the second section have been employed directly in many elegant total syntheses of complex organic structures.
Introduction
Authors: Barrett Graham c.
Published: November 2023

The common L-a-amino acids have a wide importance in synthetic organic chemistry as easily-available homochiral synthons. Thus, this book is intended to offer practical support to several areas of organic synthesis centred on amino acids, areas that are growing in importance, as shown by their continual attraction bringing in new practitioners.
Acylation and alkoxycarbonylation of the amino group
Authors: Barrett Graham c.
Published: November 2023

The various categories of reaction falling under the heading 𠄘N-acylation or N-alkoxycarbonylation of an a-amino acid𠄙 include several important synthetic processes, as well as covering the most common purposes (a) for N protection during synthesis, and (b) for the provision of samples for amino acid analysis.
Mono- and di-alkylation of the amino group
Authors: Barrett Graham c.
Published: November 2023

The prolonged reaction of an amino acid in solution with an alkyl halide leads to mixtures of secondary and tertiary amines. Continued alkylation ultimately generates the corresponding quaternary ammonium salt of the amino acid ester. This is an inefficient process in terms of organic synthesis, and reliable routes to N-alkylamino acids call for a more painstaking, less direct, approach. Reaction of an amino acid with an aldehyde, followed by reduction of the resulting alkylol or Schiff base, has been found to be reliable, although it is not often used. Weinreb and co-workers showed that simple N-hydroxymethyl amides R1conhch OH undergo acid-catalysed reductive alkylation (hydrogen-palladized charcoal) to give N-methylamides:111
Reactions at the carboxy group of an amino acid𠄔amino acid salts
Authors: Barrett Graham c.
Published: November 2023

All the standard reactions in solution involving the carboxy group are straightforward if reagents are involved that do not affect the protected or unprotected amino group and side-chain functional groups. However, solubility problems can arise that frustrate synthetic operations with underivatized amino acids, and a number of protocols are given that illustrate ways round this problem.
Reactions at the carboxy group of an amino acid𠄔esterification of amino acids
Authors: Barrett Graham c.
Published: November 2023

The conversion of the carboxy group into derivatives by acid-catalysed nucleophilic addition, or into other functional groups by reductive processes, is neither always simple nor always quantitatively successful with free amino acids as starting materials. But esterification with simple alkanols is an uncomplicated procedure. This is because amino acids will slowly dissolve in hot alkanols, and these alkanols will also dissolve a strong acid catalyst, and also because the amino group is protonated under these conditions. Without protonation, the amino group would exert its nucleophilic property and compete with nucleophilic reactions at the carbonyl carbon atom.
Synthetic uses of serine, threonine and cysteine
Authors: Meffre Patrick , Vo-Quang Liliane , Vo-Quang Yen , Goffic Francois Le
Published: November 2023

L-serine, L-threonine and L-cysteine are useful optically active precursors for the asymmetric synthesis of a wide variety of molecules such as amino acids1-3 or other nitrogen-containing targets. Commercially available, they offer a great challenge to the synthetic chemist in terms of stereochemical control and efficiency. In particular, the preparation of various serine-, threonine- and cysteine-derived aldehydes for synthetic purposes requires four conditions: Carboxy group modifications are generally undertaken after suitable protection of the OH (or SH) and NH2 functionalities. The preparation of N protected a-amino aldehydes has received much attention in recent years.13 They are usually purified by vacuum distillation,
Metal-mediated modification of the side-chains of a-amino acids
Authors: Crisp Geoffrey T
Published: November 2023

a-Amino acids are fundamental building units in biology and chemistry. For chemists, the availability of proteinogenic a-amino acids provides ready access to a pool of chiral, non-racemic synthons for further elaboration. The current awareness of the relationship between the structure and the biological activity of peptides has generated interest in new methodologies which will enable the construction of unnatural amino acids and peptides which can probe enzyme specificity and modes of recognition.
Modifications of the aryl substituents of ß-aryl a-amino acids
Authors: Barrett Graham c.
Published: November 2023

Phenylalanine and tyrosine have the conventional chemistry of benzene and phenol, respectively when their amino and carboxy groups are protected. Similarly, histidine and tryptophan have the typical behaviour of a 4-substituted imidazole and a 3-substituted indole, respectively.
Isolation and chromatographic purification of reaction products from amino acids
Authors: Oȉneil Ian a.
Published: November 2023

Functionalized amino acids are highly versatile building blocks in organic chemistry. Their ready availability and low cost has meant that they are widely used in organic synthesis. Recrystallization is often used as a method for purification, however this is not always applicable. The highly polar nature of this family of compounds means that purification by conventional flash chromatography is often difficult. In this chapter the use of a more appropriate technique, reversed-phase dry flash chromatography on a preparative scale, is reviewed. The use of reversed-phase HPLC and ion exchange chromatography will not be covered.
Equipment: the matrix-isolation cold cell
Authors: Dunkin Ian R
Published: November 2023

This chapter describes the major equipment needed for a matrix-isolation unit capable of performing various types of experiments, and gives designs of basic systems and advice on construction and maintenance. Chapter 3 deals with ancillaries, such as preparative vacuum lines, photolysis sources and spectrometers. All the items in the list above are discussed, together with some related topics. Descriptions of additional items of minor or ancillary equipment will be found in other chapters at the points where they are most relevant. Although as much helpful detail as possible has been included, there are as many ways of putting together a system as there are laboratories. Readers should thus regard the advice given about equipment as a general guide to what is needed rather than a set of immutable instructions. It is hoped that the discussion which follows will stimulate those interested in setting up a matrix laboratory to find their own most appropriate solutions.
Equipment: ancillaries
Authors: Dunkin Ian R
Published: November 2023

The construction of a matrix-isolation cold cell has been fully discussed in Chapter 2. Matrix experiments will normally also require one or more pieces of ancillary equipment.
Matrix photochemistry and spectroscopy with plane-polarized light
Authors: Dunkin Ian R
Published: November 2023

This chapter describes matrix experiments with plane-polarized light, in which molecules can be spatially oriented. Although not a major part of matrix photochemistry, the experiments are easily carried out, and can provide useful information about the symmetries of electronic and vibrational transitions and about molecular conformations. The experiments depend on the fact that, except for very small molecules, trapped species in matrices are not only prevented from diffusing but also from rotating.
Electrostatic Interactions Between Molecules
Authors: Stone A J
Published: November 2023

Suppose that molecule A is located at position A in some global coordinate system. The particles of this molecule are at positions a relative to A, i.e., at positions A+ a. We want to evaluate the potential at a point B where we shall in due course put another molecule.
Perturbation Theory Of Intermolecular Forces At Short Range
Authors: Stone A J
Published: November 2023

The perturbation theory for well-separated molecules described in Chapter 4 (the ‘longrange approximation’ or ‘polarization approximation’) is very successful if the molecules are a long distance apart, but at short range it fails completely. Part of the reason for the failure of the theory as usually formulated is that the multipole expansion breaks down, but as we have seen, the multipole expansion is not fundamental to the theory, since it is possible to use a ‘non-expanded’ treatment. We shall see in Chapter 7 how to overcome the failure of the multipole expansion to converge without resorting to this device.
Interactions Involving Excited States
Authors: Stone A J
Published: November 2023

When one of a pair of identical molecules is in an excited state, a new type of interaction becomes possible. Since either molecule can be excited, with the other in the ground state, there are two states involved, and they can mix under the influence of the inter molecular perturbation, one combination being stabilized and the other raised in energy. This effect operates at long range; there is no need for the molecular wavefunctions to overlap.
Sources Of Experimental Data
Authors: Stone A J
Published: November 2023

For the most part, this account has concentrated on methods of calculating intermolecular interactions, either analytically or from ab initio computations. However the pur pose of such calculations is to make it possible to predict the behaviour of molecules, in small aggregates or in the bulk, and in principle a knowledge of intermolecular potentials should make it possible to predict the outcome of any experiment on molecules that does not involve actual chemical reaction. Comparison of theory with experiment in cases where the result is known allows us to validate the theory and, in some cases, to calibrate unknown parameters. In this chapter we outline the experimental techniques that are useful in the study of intermolecular potentials. This is not intended to be a de tailed account; a fuller treatment may be found in the books by Gray and Gubbins (1984) and by Maitland et al. (1981).
Synthesis of a Structure Related to Hydantocidin
Authors: Hanessian S , Sanreau J -Y , Chemla, P
Published: November 2023

Discussion Points Propose a mechanism for step c with a rationalisation of the stereochemical outcome. What is the role of TBAF in step i? Further Reading For recent examples of the use of fluoride ion as a base, see: T. Sato and J. Otera, J. Org. Chem.,1995, 60,2627; see also: T. Sato and J. Otera, Synlett,1995, 845.
The Asymmetric Synthesis of Bryostatin Fragments
Authors: Brabander J De , Vandewalle, M
Published: November 2023

Discussion Points What is the purpose of the magnesium bromide etherate in step d? Propose an explanation for the observed stereochemical outcome of step g. Explain the role of the Seyferth reagent in the formation of product 6. What is the mechanism of this step?
16. Stereoselective Total Synthesis of (+)-Artemisinin
Authors: Avery M A , Chong W K M , Jennings-White, C
Published: November 2023

Discussion Points Suggest a motive for oxidising compound 2 before the alkylation step d. Explain the stereoselectivity observed in step h? What other ester could have directly afforded compound 7 via a Claisen rearrangement? Suggest a mechanism for the formation of compound 8, obtained upon ozonolysis of vinylsilane 7.
The Synthesis of (±)-Prosopinine
Authors: Cook G R , Beholz L G , Stille, J R
Published: November 2023

Discussion Points Suggest a mechanism for the annulation of alkyne 2 into the a-lactam 3. What product could be expected from the direct Baeyer-Villiger oxidation of compound 5? Propose a structure for compound 10. Compound 11 was formed in an 85: 15 mixture with its trans-isomer. Explain the selectivity of the reaction.
Total Synthesis of the Enantiomer of Hennoxazole A
Authors: Wipf P , Lim, S
Published: November 2023

Discussion Points What is the mechanism of the Evans-Mislow rearrangement in step c? Suggest a mechanism for the formation of compound 5. Explain the stereoselectivity observed in the Luche reduction step j. Further Reading For a mechanistic explanation of the selectivity of the Sharpless epoxidation, see: E. J. Corey, J. Org. Chem.,1990, 55,1693; P. G. Potvin and S. Bianchet, J. Org. Chem.,1992, 57, 6629. For reviews on the Birch reduction, see: P. W. Rabideau, Tetrahedron,1989, 45,1579; J. M. Hook and L. N. Mander, Nat. Prod. Rep.,1986, 3,35. For a review on the use of tetrapropylammonium perruthenate in organic synthesis, see: S. V. Ley, J. Norman and S. P. Marsden, Synthesis,1994, 7, 639. For an analysis of the mechanism of the Evans-Mislow rearrangement, see: D. K. Jones-Hertzog and W. L. Jorgensen, J. Org. Chem., 1995, 60, 6682; D. K. Jones-Hertzog, W. L. Jorgensen, J. Am. Chem. Soc., 1995, 117,9077.
Total Synthesis of (+)-Duocarmycin A
Authors: Boger D L , McKie J A , Nishi T , Ogiku, T
Published: November 2023

Discussion Points Step k was carried out by adding the LDA to the substrate. It was found that if the substrate was added to the base, an almost complete inversion of the newly formed quaternary stereocentre ato the imine was obtained. Suggest an explanation for this observation. Further Reading For a review on the use of allylstannanes see: E. J. Thomas, Chemtracts, 1994, 7, 207.
Total Synthesis of (+)-Pyripyropene A
Authors: Nagamitsu T , Sunazuka T , Obata R , Tomoda H , Tanaka H , Harigaya Y , Omura S , III, A B Smith
Published: November 2023

Discussion Points Explain the stereoselectivity observed in steps a and p. Give reasons for the use of the Kuwajima methylation protocol of steps d and e. What purpose does sodium thiolate serve in step I? Explain the mechanism of step o. Further Reading For the biosynthesis of pyripyropene A, see: H. Tomoda, N. Tabata, Y. Nakata, H. Nishida, T. Kaneko, R. Obata, T. Sunazuka, and S. Omura, J. Org. Chem.,1996, 61,882. For a review on the use of enol triflates in olefin synthesis, see: W. J. Scott and J. E. McMurry, Acc. Chem. Res.,1988, 21,47. For the acylation reaction of 4-hydroxy-2-pyrone, see: E. Marcus, J. F. Stephen and J. K. Chan, J. Heterocycl. Chem.,1969, 6,13.
Total Synthesis of (-)-Papuamine
Authors: McDermott T S , Mortlock A A , Heathcock, C H
Published: November 2023

Discussion Points Suggest a synthesis of starting material 1. What is the purpose of ethanolamine in the work-up of step k? What is the mechanism of step n? No coupling reaction occurred when step q was performed in the absence of Cul. Suggest a possible reason for this finding. Further Reading For a related approach to the total synthesis of (+)-papuamine, see: A. G. M. Barrett, M. L. Boys and T. L. Boehm, J. Org. Chem.,1996, 61, 685. For a review on the palladium-catalysed reaction of organotin compounds, see: T. N. Mitchell, Synthesis,1992, 9,803.
Total Synthesis of (+)-Dolabellatrienone
Authors: Corey E J , Kania, R S
Published: November 2023

Discussion Points Suggest a synthesis of chloride 1 from (E,E)-farnesol? What is the mechanism of step i? Rationalise the stereochemical outcome in terms of the stereochemistry of the starting material 6 and the intermediates formed during the transformation. What symmetry does catalyst 7 possess? What reagents would usually be employed to effect the transformation of olefin 9 into 10 ?
Total Synthesis of (+)-FR900482
Authors: Yoshino T , Nagata Y , Itoh E , Hashimoto M , Katoh T , Terashima, S
Published: November 2023

Discussion Points Apart from the high temperatures used in this synthesis, suggest alternative conditions which can be used to promote the transformation canied out in step c. What is the mechanism of step k? What are the standard conditions for the removal of a Boe protecting group from an amine? Are these conditions compatible with the deprotection of compound 10? Propose a structure for compound 12.
Total Synthesis of (+)-Acerosolide
Authors: Paquette L A , Astles, P C
Published: November 2023

Discussion Points Treatment of aldehydes with allylstannane 1 in the presence of BF3 would normally afford branched homoallylic alcohols. Suggest a mechanism for the regiochemical outcome of the reaction run in step a What relative stereochemistry is to be expected from the Nozaki reaction of step I? Further Reading For a review on the Nozaki reaction, see: P. Cintas, Synthesis,1992, 248.
The Synthesis of Picrotoxinin
Authors: Trost B M , Krische, M J
Published: November 2023

Discussion Points Propose a motive for the stereoselectivity of step c. Give a mechanism for step h. Bearing in mind the stereochemistry of epoxide 11, propose a mechanism for its acid-catalysed ring opening under the conditions of step o. Suggest a possible reason for the increased stability of five-membered ring lactone 14 compared to the six-membered ring bridged system 13.
Total Synthesis of (+)-Dactylol
Authors: Molander G , Eastwood, P R
Published: November 2023

Discussion Points Propose a mechanism for the [3 + 5] annulation step b. What is the mechanism of the Tebbe methylenation reaction? The desired product 6 was isolated in only 25% yield. Bearing in mind the mechanism of the dissolving metal ring opening reaction, suggest a structure for the major product (36%) isolated from the reaction mixture.
Synthesis of Staurosporine Aglycon
Authors: Moody C J , Rahimtoola K F , Porter B , Ross, B C
Published: November 2023

Discussion Points What is the mechanism of step b? Propose a mechanism for the transformation covered in step f. Simply refluxing compound 7 under an inert atmosphere in bromobenzene gave a product 10 in high yield. In the proton NMR spectrum of this product there were the following signals integrating for single protons; o 3.28 (dd, J= 17 and 7 Hz), o 3.69 (dd, J= 17 and 10 Hz), o 4.72 (dd, J= 10 and 7 Hz). The FAB·mass spectrum gave a protonated molecular ion at 346 mle.Suggest a structure for this compound and the motive for a second reflux of the reaction mixture in air.
A Total Synthesis of Taxol
Authors: Masters J J , Link J T , Snyder L B , Young, W B , Danishefsky, S J
Published: November 2023

Discussion Points What is the mechanism of step a? What is the purpose of aluminium triisopropoxide in step b? Give reasons for the selectivity (4:1) obtained in the osmylation step c. When fluoride ion was used instead of ethylene glycol as the desilylating agent to promote the formation of the oxetane ring in 3, the main product isolated was 12. Suggest the mechanism for its formation. Explain the diastereoselectivity observed in the formation of compound 8. Explain the stereo selectivity of epoxidation step t. Give reasons for the regioselectivity observed in the epoxide reduction step u. Suggest a way of synthesising 7.
Biological olfaction
Authors: Gardner Julian W , Bartlett Philip N
Published: November 2023

Our knowledge of the mammalian olfactory system is as yet incomplete, although spectacular progress has been made in the last few years by applying techniques from molecular biology to the problem. In this chapter we present an overview of our current knowledge of the organisation and functioning of the mammalian olfactory system at the molecular level. We also discuss the psychophysical aspects of olfaction which describe the human sensitivity and response to flavour and odour.
Electronic nose instrumentation
Authors: Gardner Julian W , Bartlett Philip N
Published: November 2023

The basic elements of a generalised electronic instrument system to measure odours are shown schematically in Fig. 8.1. First there is an odour delivery system which is designed to transfer the odour from the source material to the sensor chamber. There are two main ways in which the odour can be delivered to the sensor chamber, namely headspace sampling and flow injection. In headspace sampling, the head-space of an odorant material is physically removed from a sample vessel and inserted into the sensor chamber using either a manual or automated procedure (Section 8.2.1). Alternatively, a carrier gas can be used to carry the odorant from the sample vessel into the sensor chamber by a method called flow injection (Section 8.2.2). The sensor chamber houses the array of chosen odour sensors, e.g. semiconducting oxide, conducting polymer chemoresistors, etc. The sensor electronics not only convert the chemical signal into an electrical signal but also, usually, amplify and condition it. This can be done using conventional analogue electronic circuitry (e.g. operational amplifiers) and the output is then a set of n analogue outputs, such as Oto 5 V d.c., although a 4 to 20 mA d.c. current output is preferable if using a long cable. The signal must be converted into a digital format to be processed by a computer, and this is carried out by an analogue to digital converter (e.g. a 12-bit converter) followed by a multiplexer to produce a digital signal which either interfaces to a serial port on the microprocessor (e.g. RS-232) or a digital bus (e.g. GPIB). The microprocessor (e.g. an Intel 486 or Motorola 68HC11) is programmed to carry out a number of tasks.
Applications and case studies
Authors: Gardner Julian W , Bartlett Philip N
Published: November 2023

Electronic nose instrumentation has been used to measure both simple and complex odours in many fields of application to date. The nature of the application itself is important and there are a large number of critical factors which are important to consider. For the sake of convenience, these factors have been grouped under three distinct headings, namely the nature of the test, the measurement conditions, and. the nature of the measurand.

The nature of the test can vary considerably. For example, Table 9.1 lists a number of different kinds of tests that can be undertaken with an electronic nose.
Introduction
Authors: Ravindranath N H , Hall D O
Published: November 2023

Developing countries firmly believe that economic growth and development are necessary to reduce poverty and human deprivation. Such growth and development also offer a way of limiting unsustainable population increases; any constraints on growth could be counterproductive (WEC 1993). Thus developing countries are keen on achieving higher growth and exports. Inherent in their plans for economic expansion is the positive relationship between energy and GDP (gross domestic product). For example, the commercial energy growth rate in India during the 1980s was around 4.5 per cent (electricity at 9.2 per cent) per annum, comparable with a GDP growth rate of about 5 per cent (PC 1992). Similarly, in low-income countries generally, commercial energy consumption is growing at 3.6 per cent annually compared to a GDP growth rate of 2.5 per cent (WB 1992). What is disturbing is that the oil and electricity intensities of GDP for a country such as India are increasing even after past experiences of oil supply and price crises (TERI 1992a; OECD 1993).
Environmental impacts of biomass energy
Authors: Ravindranath N H , Hall D O
Published: November 2023

The extraction, conversion, and utilization of various forms of energy is recognized as one of the major contributors to environmental degradation at the global as well as the local level; be it greenhouse gas emissions and local air pollution due to combustion of fossil fuels, submergence of forests by hydroelectric power projects, or forest degradation due to fuel wood use.
Assessment of bioenergy programmes in India
Authors: Ravindranath N H , Hall D O
Published: November 2023

The dominance of biomass energy in the energy consumption pattern of India has been highlighted in earlier chapters. The population in India is growing at a rate of about 2.12 per cent annually and it is observed that biomass use is keeping pace with population growth. The use of biomass as a traditional fuel is associated with a lower quality of life and environmental degradation. It is thus necessary to understand what India is doing to alleviate such problems associated with the dependence on and use of biomass and to draw lessons therefrom before exploring the potential role for bioenergy in promoting sustainable development.
Land and biomass availability for sustainable bioenergy
Authors: Ravindranath N H , Hall D O
Published: November 2023

In previous chapters the potential and the technical and operational feasibility of biomass electricity systems for both decentralized village-level and megawatt level systems were shown. The utilization of this large bioenergy potential requires sustainable supplies of biomass, particularly woody biomass. Thus the woody biomass requirement, the current biomass availability, and options for sustainable supply have to be considered. In a developing country such as India the crucial question always asked is whether it would be able to simultaneously meet the food requirements of a growing population and supply biomass for energy sustainably. Food production is always a priority, and thus it is necessary to analyse the food-fuel issue and the current woody biomass production programmes with reference to India.
Implications for bioenergy in developing countries
Authors: Ravindranath N H , Hall D O
Published: November 2023

In our analysis we have shown the need and the potential for bioenergy, and the possible economic, social, and environmental benefits for India. If bioenergy options are feasible for India, a country with a high population density and poor biomass resources (low forest and pasture area per capita), it should, at least theoretically, be even more feasible for many developing countries in sub-Saharan (SS) Africa, South-East Asia, and South America, with lower population densities and larger biomass resources (Table 1.2). Although it is tempting to undertake such an analysis at the macro level for other countries, one must be acutely aware of the limitations of such an exercise, especially if there is insufficient knowledge of the individual country. However, based on our analysis for India, some broad issues on rural energy, particularly the technical potential of bioenergy in some selected developing countries, are considered. No attempt is made to make any specific recommendation for any one country.
Bioenergy: barriers, policy options, and guidelines
Authors: Ravindranath N H , Hall D O
Published: November 2023

Some of the modern bioenergy technologies have been in the portfolio of energy planners for over a decade. They have received substantial government support in countries such as Austria, Brazil, China, France, India, Sweden, USA, and Zimbabwe, to name a few. There are some successful examples from developing countries, such as the ethanol programmes in Brazil and Zimbabwe, the biogas programme in China (and to some extent in India), bagasse electricity in Mauritius, and the afforestation programme in India. However, apart from the ethanol programmes, they have yet to make significant impacts on the energy supplies in these and other developing countries. Interestingly, bioenergy technologies have made a significant entry into the energy supplies of a number of industrialized countries, such as the USA (electricity), Denmark (biogas), Sweden (combined heat and power), and Austria (heat and power and liquid fuels).
Conclusions and implications
Authors: Ravindranath N H , Hall D O
Published: November 2023

The population of the world has nearly crossed the 6 billion mark and its growth in the developing world continues to be about 2-3 per cent annually. Correspondingly, the total primary energy consumption in developing countries increased by 33 per cent between 1981 and 1991 (at 3712 Mtoe in 1991; OECD 1993). Consumption of coal increased by 56 per cent between 1982 and 1992 in developing countries (BP 1993). The fuelwood demand in developing countries is increasing and currently it is around 1.3 X 109 m3 (FAO 1993Z?) in tropical countries.
The shore environment
Authors: Little Colin , Williams Gray A , Trowbridge Cynthia D
Published: November 2023

On the Otago Peninsula, in the South Island of New Zealand, a storm rips the massive holdfasts of the giant ‘bull kelp’, Durvillaea, from the rock and Kings its fronds far up the shore. Between the jagged remnants of the holdfast the rock is left bare—but only briefly—for this area will soon be colonized by algal sporelings or invertebrate larvae. Meanwhile, the cast-up fronds provide a continuing supply of organic material for detritus feeders, as well as being broken down to provide Ine particulate material for distant suspension feeders, some on rocky shores but others on mudflats and in estuaries.

At Cape d’Aguilar, in Hong Kong, under blue skies and tropical sunshine, the tide rises and a wave splashes the rock, wetting the hordes of grazing molluscs and triggering them into activity. The limpet Cellana and the chiton Acanthopleura begin slowly moving upshore with the tide, rasping at the invisible bioIlm of micro-algae and cyanobacteria. Their grazing action maintains this rich, microbial food supply and removes the settling stages of many invertebrates. As the tide retreats, the grazers move down-shore, the limpets clamping down on vertical rock walls and the chitons seeking shelter from the heat and desiccation in shaded crevices.
Suspension feeders: how to live on floating food
Authors: Little Colin , Williams Gray A , Trowbridge Cynthia D
Published: November 2023

While the mobile grazers and predators on rocky shores may attract most attention, they are hugely outnumbered by the sessile animals—those that are Ixed in one spot. Where there is not a heavy growth of algae, the tops of rocks may be entirely covered by sheets of barnacles and mussels. On the undersides of rocks, and on many macroalgae, bryozoan colonies, ascidians, sponges, and polychaetes can form obscuring but highly diverse mats. All these species depend upon suspended food carried to them in water currents.

The distribution of sessile animals varies greatly both from shore to shore and in relation to vertical height. On wave-exposed shores in Washington (north-east PaciIc), for example, intertidal sites can be dominated by mussels such as Mytilus californianus, with patches of the sea palm Postelsia and only a scattering of barnacles. At sites of lower wave-exposure, barnacle species dominate, and where exposure is minimal, the rock supports a Fucus canopy but over 80% is free space.
Eating flesh: the predators
Authors: Little Colin , Williams Gray A , Trowbridge Cynthia D
Published: November 2023

Because of their position at the top of the food web, there are fewer predators on a rocky shore than there are grazers or suspension feeders. This does not mean, however, that predators suffer from a low diversity, and we begin by describing the variety of feeding mechanisms found among rocky shore predators.

Much of the prey available on rocky shores consists of sessile or very slow-moving animals, so many predators tend not to be as fast or mobile as their classic terrestrial counterparts. Prey have oJen adopted a ‘fortress’ strategy, attempting to defend themselves against attack. As a result, predators have developed a variety of feeding mechanisms for scaling the walls of the fortress or breaking them down.
Chronic Migraine
Authors: Wiendels N J , Ferrari M D
Published: November 2023

Chronic daily headache (CDH) is a collective term for primary headaches occurring on more than 14 days per month. The 2nd edition of the International Classification of Headache Disorders (ICHD-II) now includes four types of CDH: chronic migraine (CM), chronic tension-type headache (CTTH), new daily persistent headache (NDPH), and hemicrania continua (HC). CM is classified as a complication of migraine and is described as headache, fulfilling criteria for migraine without aura, occurring on 15 or more days per month for more than three months in the absence of medication overuse.