California red scale pheromone

California red scale pheromone Scheme 9 Vitamin Bi2-mediated Michael addition. 

Other examples include the synthesis of California Red Scale Pheromone [80], prostaglandin PGF2a [81], House Mouse Pheromone [63], and Jasmon-ates [82]. 

The homochiral f -branched carboxylic acids (13 or enf-13 Table 1) have been used for the synthesis of a variety of natural products21 such as California red scale pheromone,14 a-skytanthine,22 the southern com rootworm pheromone,15 and norpectinatone.16 Pure (5)-3-trichloromethylbutyric acid (a structural subunit of some sponge metabolites) was prepared via conjugate addition of ClaCMgCl to the chiral cro-tonate (16) followed by hydrolysis (Scheme S).23... 

In contrast, the corresponding reactions of RCu/BFa reagents (R = phenyl or alkenyl) with allylic acetals obviously proceed in an anti 5n2 fashion, as shown in (67b). The unsaturated acetals (68), prepared from (R )-butane-1,2-diol, are opened by the PBu3-stabilized reagents to give, after hydrolysis, the (3-substituted aldehydes (69) with high ee (Scheme 27).68,69 The method has been applied to the preparation of a key intermediate (85% ee) for the synthesis of the California red scale pheromone.69... 

Scheffold and colleagues subsequently reported that alkyl iodides 249 add to xfl-unsaturated esters 248 catalyzed by 23 mol% hydroxycobalamine 247 (X=OH) and mediated by light to homolyze 253B [302]. The generation of the active Co(I) species 253A proceeded by electrochemical reduction at a potential of —1.2 V vs SCE. The transformation required a large excess of 248 to promote the addition of the initially generated alkyl radical. The reaction was applied to the total synthesis of the California red scale pheromone. The product... 

B. Vitamin Bi2-mediated cyclizations California red scale pheromone, PGF2 precursor... 

B. Vitamin Bi2-Mediated Cyclizations California Red Scale Pheromone (198), PGF2 Precursor (201)... 

Vitamin B12 reacts with alkyl halides to form a cobalt(III) alkyl intermediate. Irradiation of it with visible light leads to the expulsion of a carbon-centered radical and a cobalt(II) species. The latter is easily reduced electrochemically at —0.8 V to reconvert it to a cobalt(I) species that reenters the catalytic cycle by reacting with a second molecule of the halide [45]. The radical is capable of undergoing a variety of interesting transformations, including conjugate addition to a Michael acceptor (e.g., 196), as is illustrated in Eq. (37), leading to the synthesis of the California red scale pheromone (198). 

Figure 4.22. Natural products synthesized by asymmetric 1,4-addition of cuprates to esters citronellic acid [124] California red scale pheromone [129] mycolipenic acid (W. Oppolzer T. Godel, unpublished, quoted in [130]) the alleged norpectinatone [128] vitamin E side chain (W. Oppolzer R. Moretti, unpublished, quoted in [ 130]) southern com rootworm pheromone...

These features have been applied to a simple synthesis of California red scale pheromone starting from the benzothiazole sulfide/benzyl ether of (5)-(—)-citronellol (eq 4). 

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