In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl group of one amino acid to the amino group of another. Protecting group strategies are usually necessary to prevent undesirable side reactions with the various amino acid side chains. Chemical peptide synthesis most commonly starts at the carboxyl end of the peptide (C-terminus), and proceeds toward the amino-terminus (N-terminus). Protein biosynthesis in living organisms occurs in the opposite direction.
The Nicolaou Taxol total synthesis, published by K. C. Nicolaou and his group in 1994 concerns the total synthesis of taxol. Taxol is an important drug in the treatment of cancer but also expensive because the compound is harvested from a scarce resource, namely the pacific yew.
The Danishefsky Taxol total synthesis in organic chemistry is an important third Taxol synthesis published by the group of Samuel Danishefsky in 1996 two years after the first two efforts described in the Holton Taxol total synthesis and the Nicolaou Taxol total synthesis. Combined they provide a good insight in the application of organic chemistry in total synthesis.
The Masamune-Bergman cyclization or Masamune-Bergman reaction or Masamune-Bergman cycloaromatization is an organic reaction and more specifically a rearrangement reaction taking place when an enediyne is heated in presence of a suitable hydrogen donor. It is the most famous and well-studied member of the general class of cycloaromatization reactions. It is named for Japanese-American chemist Satoru Masamune and American chemist Robert G. Bergman. The reaction product is a derivative of benzene.
The Negishi coupling is a widely employed transition metal catalyzed cross-coupling reaction. The reaction couples organic halides or triflates with organozinc compounds, forming carbon-carbon bonds (C-C) in the process. A palladium (0) species is generally utilized as the metal catalyst, though nickel is sometimes used. A variety of nickel catalysts in either Ni0 or NiII oxidation state can be employed in Negishi cross couplings such as Ni(PPh3)4, Ni(acac)2, Ni(COD)2 etc.
The calicheamicins are a class of enediyne antitumor antibiotics derived from the bacterium Micromonospora echinospora, with calicheamicin γ1 being the most notable. It was isolated originally in the mid-1980s from the chalky soil, or "caliche pits", located in Kerrville, Texas. The sample was collected by a scientist working for Lederle Labs. It is extremely toxic to all cells and, in 2000, a CD33 antigen-targeted immunoconjugate N-acetyl dimethyl hydrazide calicheamicin was developed and marketed as targeted therapy against the non-solid tumor cancer acute myeloid leukemia (AML). A second calicheamicin-linked monoclonal antibody, inotuzumab ozogamicin an anti-CD22-directed antibody-drug conjugate, was approved by the U.S. Food and Drug Administration on August 17, 2017, for use in the treatment of adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia. Calicheamicin γ1 and the related enediyne esperamicin are the two of the most potent antitumor agents known.
Robert S. Coleman is an American chemistry professor and researcher. Coleman was a faculty member at both Ohio State University and the University of South Carolina. At Ohio State, he was on the faculty in the Department of Chemistry from 1996 to 2012, having moved to Ohio State as an associate professor from the University of South Carolina. At USC, Coleman taught as assistant professor from 1989 to 1995, and then as associate professor from 1995 to 1996. In 1996, he accepted a faculty position at Ohio State University to teach Organic Chemistry, where he was an associate professor from 1996 until 2000. He was promoted to full professor in 2000, teaching Organic Chemistry up until his retirement in 2012. He received his Ph.D. degree working with Professor Dale L. Boger, completing the first total synthesis of the antitumor agent CC-1065. He was subsequently an NIH postdoctoral fellow at Yale University with Professor Samuel J. Danishefsky, where he completed, the first total synthesis of the aglycone of the antitumor agent calicheamicin.
Thiostrepton is a natural cyclic oligopeptide antibiotic of the thiopeptide class, derived from several strains of streptomycetes, such as Streptomyces azureus and Streptomyces laurentii. Thiostrepton is a natural product of the ribosomally synthesized and post-translationally modified peptide (RiPP) class.
Enediynes are organic compounds containing two triple bonds and one double bond.
Kinamycins are a group of bacterial polyketide secondary metabolites containing a diazo group. Kinamycins are known for their cytotoxicity and are considered of interest for potential use in anti-cancer therapies.
Dynemicin A is an anti-cancer enediyne drug. It displays properties which illustrate promise for cancer treatments, but still requires further research.
Free radical damage to DNA can occur as a result of exposure to ionizing radiation or to radiomimetic compounds. Damage to DNA as a result of free radical attack is called indirect DNA damage because the radicals formed can diffuse throughout the body and affect other organs. Malignant melanoma can be caused by indirect DNA damage because it is found in parts of the body not exposed to sunlight. DNA is vulnerable to radical attack because of the very labile hydrogens that can be abstracted and the prevalence of double bonds in the DNA bases that free radicals can easily add to.
Secalonic acids are a group of chiral dimeric tetrahydroxanthones closely related to ergoflavin and ergochrysin A that are collectively called ergochromes and belong to a class of mycotoxins initially isolated as major ergot pigments from the fungi Claviceps purpurea that grows parasitically on rye grasses. From early times and particularly in medieval Europe the consumption of grains containing ergot has repeatedly lead to mass poisonings known as ergotism which was caused by toxic ergot alkaloids and mycotoxins such as the ergochromes, due to contamination of flour by C. purpurea. A cluster of genes responsible for the synthesis of secalonic acids in C. purpurea has been identified. Secalonic acid D the enantiomer of secalonic acid A is a major environmental toxin, isolated from the fungus Penicillium oxalicum, and is a major microbial contaminant of freshly-harvested corn which causes toxicity through contamination of foodstuffs.
Eudistomins are β-carboline derivatives, isolated from ascidians, like Ritterella sigillinoides, Lissoclinum fragile, or Pseudodistoma aureum.
Lavendamycin is a naturally occurring chemical compound discovered in fermentation broth of the soil bacterium Streptomyces lavendulae. Lavendamycin has antibiotic properties and anti-proliferative effects against several cancer cell lines. The use of lavendamycin as a cytotoxic agent in cancer therapy failed due to poor water solubility and non-specific cytotoxicity. The study of lavendamycin-based analogs designed to overcome these liabilities has been an area of research.
Kedarcidin is a chromoprotein antitumor antibiotic first isolated from an Actinomycete in 1992, comprising an ansa-bridged enediyne chromophore (shown) as well as an apoprotein that serves to stabilize the toxin in the Actinomycete. Like other members of the enediyne class of drugs—so named for the nine-or-ten-membered core structure bearing an alkene directly attached to two alkynyl appendages—kedarcidin was likely evolved to kill bacteria that compete with the producing organism. Because it achieves this by causing DNA damage, however, kedarcidin is capable of harming tumor cells, as well. Kedarcidin is thus the subject of scientific research, both for its structural complexity as well as its anticancer properties.
Poly(amidoamine), or PAMAM, is a class of dendrimer which is made of repetitively branched subunits of amide and amine functionality. PAMAM dendrimers, sometimes referred to by the trade name Starburst, have been extensively studied since their synthesis in 1985, and represent the most well-characterized dendrimer family as well as the first to be commercialized. Like other dendrimers, PAMAMs have a sphere-like shape overall, and are typified by an internal molecular architecture consisting of tree-like branching, with each outward 'layer', or generation, containing exponentially more branching points. This branched architecture distinguishes PAMAMs and other dendrimers from traditional polymers, as it allows for low polydispersity and a high level of structural control during synthesis, and gives rise to a large number of surface sites relative to the total molecular volume. Moreover, PAMAM dendrimers exhibit greater biocompatibility than other dendrimer families, perhaps due to the combination of surface amines and interior amide bonds; these bonding motifs are highly reminiscent of innate biological chemistry and endow PAMAM dendrimers with properties similar to that of globular proteins. The relative ease/low cost of synthesis of PAMAM dendrimers (especially relative to similarly-sized biological molecules such as proteins and antibodies), along with their biocompatibility, structural control, and functionalizability, have made PAMAMs viable candidates for application in drug development, biochemistry, and nanotechnology.
Didemnum fragile is a species of sea squirt in the family Didemnidae.
C-1027 or lidamycin is an antitumor antibiotic consisting of a complex of an enediyne chromophore and an apoprotein. It shows antibiotic activity against most Gram-positive bacteria. It is one of the most potent cytotoxic molecules known, due to its induction of a higher ratio of DNA double-strand breaks than single-strand breaks.
Richmond Sarpong is a Ghanaian-American chemist who is a professor at the University of California, Berkeley. Sarpong works on natural product total synthesis to better understand biological systems and allow for the development of novel therapeutics. He was awarded a Guggenheim Fellowship in 2017, and was elected a fellow of the American Academy of Arts and Sciences in 2020. He serves on the editorial boards of Organic Syntheses, Accounts of Chemical Research and Synlett.
