Appendagitis

A partially cross-linked, isobutylene—isoprene—divinylbenzene terpolymer containing some unreacted substituted vinylbenzene appendages is commercially available from Polysar Division, Bayer AG. Because of the residual reactive functionality, it can be cross-linked by peroxides that degrade conventional butyl mbbets. It is employed primarily in the manufacture of sealant tapes and caulking compounds (31). 

Additional keying information can come from certain other structural features which are present in a retron- or partial-retron-containing substructure. These ancillary keying elements can consist of functional groups, stereocenters, rings or appendages. Consider target structure 5... 

Disconnections which leave stereocenters on newly created appendages are not strategic unless the stereocenters can be removed with stereocontrol prior to the disconnection (see section 4.3). 

If the disconnection of a bond found to be strategic by criteria 1-3 produces a new ring appendage bearing stereocenters, those centers should be removed if possible (by stereocontrolled transforms) before the disconnection is made. 

Functional Groups and Appendages as Keys for Connective Transforms.71... 

The Y appendage of 2-cyclohexenone 191 cannot be directly disconnected by an alkylation transform. (y-Extended enolates derived from 2-cyclohexenones undergo alkylation a- rather than y- to the carbonyl group). However, 191 can be converted to 192 by application of the retro-Michael transform. The synthesis of 192 from methoxybenzene by way of the Birch reduction product 193 is straightforward. Another synthesis of 191 (free acid) is outlined in... 

A pair of appendages which are in spatial proximity suggests the application of connective transforms, even if such appendages are not functionalized. Typical of retrosynthetic connections of this type are those shown for targets 201 and 202. ... 

Algorithms for machine-generated syntheses by application of connective transforms to target structures containing appendages, medium-sized rings, etc. have been described. ... 

Appendage. A structural subunit consisting of one or more carbon atoms and their substituents which is bonded to a ring or functional group origin. 

The synthesis of ovalicin was accomplished following a line of analysis which was totally different from that employed for the synthesis of the structural relative fumagillol. The plan for ovalicin was based on S-goal, appendage, stereochemical and functional group derived strategies. A key requirement for the synthesis was the stereospecific construction of the -l,4-pentadienyl subunit, which was achieved by a method of potentially wide utility. 

Tricyclohexaprenol, a possible forerunner of sterols in the evolution of biomembranes, was synthesized by construction of the cyclic network in one step using cation-olefin tricyclization and subsequent stereocontroUed attachment of the Cio appendage to ring C. 

A chemical synthesis of prostaglandins by a free radical pathway through an endoperoxide intermediate showed a strong stereochemical preference for the formation of the endoperoxides having cis alpha and omega appendages. 

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