Cyclohexyl fragments

M. E. Maier and B. Schooling, Synthesis of the cyclohexyl fragment of FK-506 by intramolecular ene-reaction, Tetrahedron Lett. 37 3007 (1990). 

The cyclohexyl fragment of FK-506 (Scheme 6.62) [85] and la,25-dihydroxy-Vitamin D3 Ring A synthon (Scheme 6.63) [87] were readily accessible by trans- and cis-selective cychzation, respectively. 

The reactivities of tertiary C—H bonds in Pr and cyclohexyl fragments of i-propylcyclohexyl benzene were determined in the liquid-phase oxidations of isopropylbenzene, cyclohexylbenzene, and isopropylcyclohexylbenzene in the presence of azobis(isobutyronitrile). The subsequent formation of mono- and di-hydroperoxides was considered, and a kinetic model for /-propylcyclohexylbenzene oxidation was proposed. ... 

The (partial) description of the synthesis and coupling of the five fragments starts with the cyclohexyl moiety C —C. The first step involved the enantio- and diastereoselective harpless epoxidation of l,4-pentadien-3-ol described on p. 126f. The epoxide was converted in four steps to a d-vinyl d-lactone which gave a 3-cyclohexenecarboxylate via Ireland-CIaisen rearrangement (cf. p. 87). Uncatalysed hydroboration and oxidation (cf. p. 131) yielded the desired trans-2-methoxycyclohexanol which was protected as a silyl ether. The methyl car-... 

A saturated ring with an aliphatic side chain favors cleavage at the bond connecting the ring to the rest of the molecule. Compounds containing cyclohexyl rings fragment at m/z 83, 82, and 81, corre-... 

Calf thymus (CT) DNA was first fragmented by sonication, then purified by a standard procedure. Agarose gel electrophoresis for the sonicated CT DNA revealed a distribution in molecular weight ranging from 30 kDa to 260 kDa which is equivalent in base pairs (bp) from 40 to 400 (1 bp = 660 Da). The DNA fragments were reacted with HEDS in the presence of l-cyclohexyl-3-(2-morpholinoethyl) carbodi-imide metho-p-toluenesulfonate (CMC/jTs). Finally, the reaction mixture was gel-filtered and the macro-molecular fractions, when displayed the characteristic absorption of 260 nm of the nucleic bases, were collected. 

The same strategy as for the synthesis of 40 has been employed for the preparation of the Li/Sn-mixed cluster 41. Thus, replacement of the imido groups in [Sn(NtBu)]4 with LiPHR (R = cyclohexyl) in the molar ratio of 4 6 yielded the metallacyclic cage complex 41, which has a rhombododecahedral Li4Sn4P6 core (Eq. 24) (69). The clusters 40 and 41 are isostructural, since the MeAl fragments in 40 have been replaced by the isoelectronic Sn(II) centers. 

Two conceptually different approaches to the tra 5-4-cyclohexylproline fragment have been disclosed by the Squibb process group. The first route relies on a stereoselective alkylation for installation of the cyclohexyl substituent (Thottathil et al., 1986). L-Pyroglutamic acid (62) was reduced using literature methods to give the hydroxymethyl... 

The fragmentation route of hydroxy-1,4-biradicals could be effectively removed as a viable possibility by replacing the cyclohexyl rings of 82 with a 1-adamantyl group the 1-adamantene which would be formed violates... 

As an initial exercise consider die syndiesis of C from cyclohexyl bromide. First one has to note relevant facts about die target, such as (a) it contains an ester and (b) it has two more carbons than the starting material so a two-carbon fragment will have to be attached by a new carbon-carbon bond. 

A syn displacement of the bromine by benzylamine in the presence of triethylamine led, by a Sn2 reaction, to the a and p amino compounds which were separated into 326 (18%) and 327 (81%) respectively. The dichloroacetamide 328 derived from the latter, when subjected to the action of tri-n-butyltinhydride (2eq) and 2,2 -azobisisobutyronitrile underwent a 5-ero ring closure to furnish via the radical 329, the hydrooxindole 330 (51%) and significant amount of the rearrangement product 331 (30%). The latter is believed to be formed by fragmentation of the cyclohexadienyl radical 332 generated from the cyclohexyl radical 329. On diborane reduction, 330 provided the cis hydroindole 333, which on 0,N-debenzylation afforded ( )-c -fused bicyclic aminoalcohol 334, a compound that had been previously cyclised with formaldehyde to ( )-elwesine (320) by Stevens et al [85]. 

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