The past decade of organic chemistry may be charcterized as a period of violent development of new synthetic methods. This was accompained by a systematization of the analysis of synthetic problems (synthetic strategy). The planning of the synthesis of an organic target molecule is greatly facilitated by distinguishing between reagents X(C)n … with normal reactivity (acceptor properties at C1,3,5…, donor properties at X, C2,4…) and with reactivity umpolung (acceptor properties at X, C2,4…, donor properties at C1,3,5…). In this context, reactivity umpolung turned out to be useful as a heuristic principle, as a classification scheme, and as an aid for locating so-called strategic bonds (synthon, transform, and antithesis according to E. J. Corey). There are six principal methods of umpolung: 1 2n-oxidation, heteroatom exchange and modification, homologation and its reversal, the cyclopropane “trick”, use of acetylenes, and redox reactions; under certain circumstances none of these techniques is necessary in cases where direct umpolung is possible. Throughout the article, normal reactivity is indicated by green print; reactivity umpolung by red print.

Methods of Reactivity Umpolung

CHAPTER 3 – Photosensitized Oxidation and Singlet Oxygen: Consequences in Biological Systems

INTRODtTCTION ... .. .... . . ........ . . . . ....... . . . ... .. .. . .. . . .... . . . .. ... ....... .. . .. .. . . .... .. . .. .. . . ... . . . . 74 OXYGEN ACTIVATION AND REACTIVE OXYGEN SPECIES ... ..... . . . . . ..... . .. ... 75 Reductive Activation ........ . . ......... ... . . . ..... . ..... .. ....... . . . . .. ....... . . . . 75 Oxygen Addition to Organic Radicals or Reduced Metal Complexes 75 Photodynamic Reactions ,.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . . 76 REACTIVITY AND DETECTION OF ACTIVE OXYGEN SPECIES 77 Superoxide . . . . . ... . . . . ....... . . . . . . . . ....... . . . . . . . . ..... ......... ..... 77 Hydrogen Peroxide (H20JJ 77 The OR Radical ....... . . 78 Singlet Oxygen 78 Organic Peroxides and Peroxy Radicals ......... . . . . . 79 OXYGEN ACTIVATION IN DIFFERENT COMPARTMENTS AND ORGANELLES OF PLANT CELLS 79 Peroxides in Cell Walls . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Microsomal Oxygen Activation .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Peroxisomes ........ . . . . . . . . . . . . . . . . . . . . . . ....... . . . . . . . . . . . . . ..... ...... 80 Oxygen Activation and Detoxification in Mitochondria . ...... 80 Chloroplasts ....... .... ...... ..... .. . . . ..... . . . ...... . . . . . . . . ..... . . . . . ......... . ... 81 Physiological observations and the biological significance of oxygen reduction 8 1 Mechanisms o f oxygen activation in the chloroplast .... ..... 82 Functions of activated oxygen species in chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 84 ENDOGENOUS MECHANISMS OF PROTECTION AGAINST DELETERIOUS OXYGEN SPECIES ...... 84 PATHOLOGICAL, ENVIRONMENTAL, AND COMMERCIAL ASPECTS OF OXYGEN TOXICITy 86 CONCLUDING REMARKS AND FUTURE TRENDS 88

Oxygen activation and oxygen toxicity

In den letzten zehn Jahren haben sich die organisch-chemischen Synthesemethoden sturmisch entwickelt. Parallel dazu ist die Analyse synthetischer Probleme systematisiert worden (Syntheseplanung). Die Aufstellung eines Syntheseplans fur ein organisches Zielmolekul wird durch die Unterscheidung von Reagentien X(C)n … normaler Reaktivitat (Acceptoreigenschaften an C1, 3, 5 …, Donoreigenschaften an X, C2, 4…) und umgepolter Reaktivitat (Acceptoreigenschaften an X, C2, 4 …, Donoreigenschaften an C1, 3, 5 …) bedeutend erleichtert. Die Umpolung der Reaktivitat wurde als nutzliches heuristisches Prinzip, als Einteilungsschema und als Leitfaden zum Auffinden strategischer Bindungen erkannt (Synthon-, Transform- und Retrosynthesebetrachtungen nach Corey). Die Methoden der Umpolung lassen sich in sechs Gruppen einteilen: die 1, 2n-Oxidation, den Heteroatom-Austausch, die Homologisierung und ihre Umkehr, den Cyclopropan-„Trick”, die Verwendung von Acetylenen und die Redoxreaktionen; die in speziellen Fallen mogliche, direkte Umpolung kommt ohne diese Methoden aus. – In diesem Aufsatz wird die normale Reaktivitat durch grunen Druck, die umgepolte Reaktivitat durch roten Druck gekennzeichnet.

Methoden der Reaktivitätsumpolung

The role of superoxide anion- and myeloperoxidase-dependent reactions in the light emission by phagocytosing polymorphonuclear leukocytes has been investigated using leukocytes that lack myeloperoxidase, inhibitors (azide, superoxide dismutase), and model systems. Our earlier finding that oxygen consumption, glucose C-1 oxidation, and formate oxidation are greater in polymorphonuclear leukocytes that lack myeloperoxidase than in normal cells during phagocytosis has been confirmed with leukocytes from two newly described myeloperoxidase-deficient siblings. Although the maximal rate of superoxide anion production by myeloperoxidase-deficient leukocytes is not significantly different from that of normal cells, superoxide production falls off less rapidly with time so that with prolonged incubation, it is greater in myeloperoxidase-deficient than in normal cells. Chemiluminescence by myeloperoxidase-deficient leukocytes during the early postphagocytic period however is decreased. Light emission by normal leukocytes is strongly inhibited by both superoxide dismutase and azide, whereas that of myeloperoxidase-deficient leukocytes, while still strongly inhibited by superoxide dismutase is considerably less sensitive to azide. Zymosan, the phagocytic particle employed in the intact cell system, considerably increased the chemiluminescence of a cell-free superoxide-H2O2 generating system (xanthine-xanthine oxidase) and a system containing myeloperoxidase, H2O2, and chloride. Light emission by the xanthine oxidase model system is strongly inhibited by superoxide dismutase and is not inhibited by azide, whereas the myeloperoxidase-dependent model system is strongly inhibited by azide but only slightly inhibited by superoxide dismutase. These findings suggest that light emission by phagocytosing polymorphonuclear leukocytes is dependent on both myeloperoxidase-catalyzed reactions and the superoxide anion, and involves in part the excitation of the ingested particle. These studies are discussed in relation to the role of the superoxide anion and chemiluminescence in the microbicidal activity of the polymorphonuclear leukocyte.

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Kenneth L. Kees

Papers

Titanium-induced reductive coupling of carbonyls to olefins

Synthesis of cycloalkenes by intramolecular titanium-induced dicarbonyl coupling

Singlet molecular oxygen in biological systems: non-quenching of singlet oxygen-mediated chemiluminescence by superoxide dismutase.

1-Phospha-2,8,9-trioxaadamantane ozonide. Convenient source of singlet molecular oxygen