Chemical defense agents

In this review, we use the terms, biologically active or bioactive for any substance which elicits some biological response in another organism. Early investigations on bioactive marine isonitriles focussed on compounds that might serve as chemical defense agents (cf. Sect. 5.1). As chemists began to resolve mixtures into individual components, other tests related to antiviral, antimicrobial, or antiparasitic activity, were reported. Often, bioassays were performed... 

One of the most intriguing newly discovered natural organohalogens is l-chloro-3-methyl-2-butene (9) from a secretion of a male flying fox (Pteropus giganteus) (380). Since this compound is known to be a powerful lachrymator (personal experience), it may function as a chemical defensive agent ( allomone ) for the fox. 

The first example of a halogenated bipyrrole was the marine bacterium Chromobacterium sp. metabolite 35 <74MB281>. Both nudibranchs (sea slugs) and bryozoans (moss animals) secrete brominated bipyrroles ("tambjamines") as chemical defensive agents. Some recent examples from the bryozoan Bugula dentata are tambjamines G-J (36-39) <94AJC1625>. 

Termite soldiers produce a large number of different chemical defense agents. Several of these molecules are unusual bioactive terpenoids such as the secotrinervitanes that have been isolated and their structure elucidated. In the laboratory of T. Kato, the total synthesis of (+)-3a-acetoxy-7,16-secotrinervita-7,11-dien-15P-ol was accomplished. The Nagata hydrocyanation was used to introduce a carbon at the P-position of a macrocyclic enone intermediate. The substrate was treated with excess diethylaluminum cyanide in dry toluene and the addition resulted in the formation of a 1 1 mixture of diastereomers, which could be readily separated by column chromatography. The cyano group was later converted to the corresponding methyl ester. 

In addition to serving as chemical defense agents, polyketides also play essential roles in the growth and development of different organisms. For example, volatile bicyclic acetals from caddisflies serve as important intra- and... 

The brightly colored and delicately shaped nudibranchs form the largest order in the subclass Opisthobranchia. As they lack an external shell these animals are not protected physically from their predators, but nevertheless the nudibranchs are rarely eaten by fish. There have been many studies of their defence mechanism. Some of the animals exude a strongly acidic skin secretion, other species are reported to secrete toxic or noxious substances. Nudibranchs feed on sponges as well as on coelenterates and bryozoans, and it has been demonstrated that they selectively accumulate chemical defensive agents from their... 

In a defensive strategy that is based on the detection of a chemical/biological agent in order to initiate a response, the time required for authorities to respond to an attack has three components the inherent response time of the detection system, the time required to verify the validity of a detector alarm, and the time required to decide on what action to take in response to the alarm. These three elements are discussed in more detail below. 

MOCVD as, 22 153-154 in silicon carbide fiber manufacture, 22 534 thermally activated, 24 744-745 Chemical vapor infiltration (CVI), 26 767 ceramics and, 5 664 Chemical warfare, 5 813-840 defense against, 5 830-837 Chemical warfare agents, detection of, 22 716-717... 

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