Yamaguchi protocol

In a recent work, Marx and collaborators presented a protocol to calculate the dynamics of the coupling constant KAB(t) on the basis of an improved Yamaguchi expression that incorporated spin projection in a Hubbard-corrected two-determinant approach to obtain more accurate KAB values (86,87). 

Variations in the Yamaguchi protocol also involve differing the order of addition. For example, in the synthetic studies toward bafilomycin A, the Cl-Cll and C12-C17 fragments were coupled by first premixing the acid 15 with DMAP (2 eq.) in toluene at room temperature, then adding triethylamine (4 eq.) and 2,4,6-trichlorobenzoyl chloride (2 eq.) successively, then finally adding the alcohol 16 in toluene.16 An excellent yield was obtained. 

Due to the prevalence of many macrolide natural products, Yamaguchi s esterification has been used extensively in the total syntheses of such compounds. Increasingly, Yamaguchi s method has succeeded where other notable esterification conditions have failed. A recent example involves the coupling of two monomers to form the clavosolide A dimer.17 The Corey-Nicolaou protocol mentioned previously gave only a 30% conversion whereas the Yamaguchi esterification resulted in a clean reaction with a 66% yield. 

In a remarkable experiment (scheme 5) S. F prepared diglycosidated seco acid 17 from 2 Martin and M. Yamashita [13] have parted via partial synthesis in ten steps and subjected with the accepted philosophy of erythromycin it to Yamaguchi s macrolactonization conditi-synthesis, namely to perform first the lactoni- ons. However, this protocol afforded only zation and then the glycosidation. They minor amounts of the desired macrolide 18,... 

Recently, Shishido has achieved the third total synthesis of (+)-lasonolide A, and their synthetic strategy was based on the introduction of the side chain via Lee s protocol, the successful Yamaguchi macrolactonization, and the... 

Yamaguchi N, Winter CM, Wu MF, Kwon CS, WilKam DA, Wagner D (2014) PROTOCOLS chromatin immunoprecipitation from arabi-dopsis tissues. The Arabidopsis book. Am Soc Plant Biol 12 e0170. doi 10.1199/tab.0170... 

Extension of the traditional Yamaguchi/Corey-Nicolaou/Keck macrolactonization protocols (see Scheme 2.1) [5] to catalytic variants can address some of the drawbacks of classical methods. Mixed anhydrides can undergo cyclization with Lewis adds such as Sc,1i, Zr, and Hf [125,126].Trostetol. reported the use of ethoxyacetylene as a stoichiometric activating agent, installed via Ru catalysis [127], later applied to the synthesis of apicularen A (Scheme 2.67) [128]. 

Yamaguchi investigated the utility of a mixed anhydride composed of the 2,4,6-trichlorobenzoate moiety, which was generated from 2,4,6-trichlorobenzoyl chloride with EtjN (triethyl amine) [26]. Thermodynamic activation of the bulky mixed anhydride in the presence of DMAP (4-dimethylaminopyridine) afforded the corresponding lactones in good yields. Yamaguchi then used this methodology to synthesize methynolide (18), as depicted in Scheme 5.4 [27], and over 340 examples of the application of this procedure showed the usefulness of the protocol [17]. 

Aggarwal performed the stereoselective total synthesis of solandelactones E and F by a stereocontrolled allylboration reaction of the eight-membered lactone 83, which was prepared by cyclization of 81 (Scheme 5.28) [76]. Treatment of the seco-acid 81 under Yamaguchi conditions according to the protocol previously established by Martin et al. [73] and Pietruszka [75] for a similar reaction resulted in the formation of the target lactone 82 in good yield. 

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