Jan Spengler

15 and 30-Membered polyolefinic macrocycles. Periphery modification by aromatic nucleophilic substitution of fluorine

Abstract Tris[(4-fluorophenyl)sulfonyl]-1,6,11-triazacyclopentadeca-3,8,13-triene is a pivotal 15-membered triolefinic macrocycle from which a vast array of different derivatives are prepared by substitution of fluorine atoms.

Preparation of nitrogen-containing 20-membered tetraolefinic macrocycles: (E,E,E,E)-1,6,11,16-tetra(arylsulfonyl)-1,6,11,16-tetraazacycloicosa-3,8,13,18-tetraenes

Abstract Arenesulfonamides and trans -1,4-dibromobut-2-ene are the ultimate precursors for the stepwise preparation of the 20-membered macrocycles of the title.

A Novel Protecting/Activating Strategy for β-Hydroxy Acids and Its Use in Convergent Peptide Synthesis

beta-Hydroxy acids were reacted with hexafluoroacetone and carbodiimides to give carboxy-activated six-membered lactones in good yields. On reaction with amines, the corresponding amides were obtained. We demonstrate the following applications of this protecting/activating strategy: preparation of carboxamides in solution and on solid phase (both normal and reverse mode); recovery and reuse of the excess material in solid-phase synthesis; and convergent solid-phase peptide synthesis (CSPPS) with peptide segments bearing C-terminal Ser or Thr with very low levels of epimerization (<1%, HPLC).

A New Approach toN-Methylaspartic,N-Methylglutamic, andN-Methyl-α-aminoadipic Acid Derivatives

N-Methylaspartic acid derivatives and its homologues are obtained by a stereoconservative one-pot procedure from hexafluoroacetone-protected aspartic and glutamic acid, 2a and 2b, respectively. α-Aminoadipic acid (5c) and its derivative 6c are accessible from the corresponding glutamic acid derivative 9b by a Wolff rearrangement. A variety of homochiral N-methylamino acids, 5 and 12, and their derivatives, 6 and 8-11, become readily available by the new synthetic concept.

One-Pot Peptide Ligation–Oxidative Cyclization Protocol for the Preparation of Short-/Medium-Size Disulfide Cyclopeptides

Native chemical ligation (NCL) employing the N-methylbenzimidazolinone (MeNbz) linker readily provided the linear precursor of a 16-mer peptide that is difficult to obtain by stepwise solid-phase peptide synthesis. NCL and the workup conditions were improved toward a protocol that allows for quantitative removal of the 4-hydroxymercaptophenol additive and subsequent formation of the disulfide bridge in the NCL cocktail by oxidation in air, tolerated by the presence of tris(hydroxypropyl)phosphine.

Advances in Organic Synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules often contain a higher level of complexity than purely inorganic compounds, so that the synthesis of organic compounds has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: total synthesis, semi-synthesis, and methodology. A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available (petrochemical) or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a linear synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. For more complex molecules, a convergent synthetic approach may be preferable, one that involves individual preparation of several “pieces” (key intermediates), which are then combined to form the desired product. n n n xa0 n n n In the present book, ten typical literatures about organic synthesis published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on organic chemical, organic compound, science, ect. We hope this book can demonstrate advances in organic synthesis as well as give references to the researchers, students and other related people.