S -fragment

With only few exceptions, most log P programs refer to the octanol-water system. Based on Rekker s fragmental constant approach, a log P calculation for aliphatic hydrocarbon-water partitioning has been reported [96]. Another more recent approach to alkane-water log P and log D is based on the program VolSurf [97]. It is believed that these values may offer a better predictor for uptake in the brain. 

To our knowledge only in a single publication [18] was a better correlation of PSA with drug transport reported after inclusion of S fragments. 

Remarkably, alkylation of the core of a dendrimer of generation 6 (two P = N-P(S) fragments on the core, 64 for the fifth generation, and an upper generation incorporating 256 terminal aldehyde groups) can be performed. This clearly demonstrates that the core of this sixth generation dendrimer is available for certain reactions. 

Table VI contains the geometric parameters of the main structural (+)E15-C-E14-S(-) fragment found by the calculation for several betaines I, which were studied by us using X-ray analysis (see Section 3). The X-ray data are presented in parentheses.

Geometric Parameters of the <+)E15-C-E14-S< ) Fragment for Several Betaines I with the Thiolate Center According to DFT... 

Table 2. Iminoboranes for which details of m.s. fragmentation have been published...

Fig. 7. Estimates of the logarithm of partition coefficient in octanol water (log P) of 4-PIOL analog substituents obtained by use of Crippen s fragmentation method. Correlation between affinity tpAT,) and lipophilicity (log P) of the substituents of the 4-PIOL analogs. The two gray lines connect the high-affinity compounds (open squares) and the low-affinity compounds (open triangles), respectively, and the black line shows the correlation between the remaining compounds (black circles).

As a second step in the reaction, following co-ordination, most authors propose an oxidative addition of the C-S fragments to the transition metal, similar to the reaction found for carbon-to-phosphorus bond breaking. Since the C-S bond is rather weak it is easy to break and indeed several model reactions can be found in the literature. 

Sekiguchi, O. Noguchi, T. Ogino, K. Tajima, S. Fragmentation of Metastable Molecular Ions of Acetylanisoles. Int. J. Mass Spectrom. Ion Proc. 1994, 132, 172-179. 

Only two syntheses use different approaches from the reaction of N-C-C-S and C-C fragments. In the first one, an isothiocyanate was used to supply a C-S fragment (Scheme 67) <1988ZC58>. In the second synthesis, compound 286 reacted three times as an electrophile (Scheme 68) <2006EJOI555>. 

Flammability Index — 138 seconds. Its definition is given in this Vol, under F s Fragmentation Test Sample of 95/5-EDNA/... 

Not unexpectedly, the [FeH(CO)4] anion aggregates with photochemi-cally generated [M(CO)s] fragments (M = Cr, Mo, or W) to give the [FeMH(CO)9] anions.5 These anions have interesting structures and reactivities, and can serve as useful precursors to the heterobimetallic anions [FeM(CO)9]2, 5. A preparation of the latter dianions, based on the reaction of Na2 [Cr(CO)5] and Fe2(CO)9, is available.6 However, problems of separation and purification are considerably alleviated in the following procedures. 

All four anions are similarly constructed from a planar Ni -(CO)sip2-CO)e fragment of D3h-62m symmetry capped by two Nis(CO)s(p2-CO)s fragments through Ni-Ni interactions. 

K. Yamanouchi In the VUV-PHOFEX measurements, the photofragment of S( S) was monitored by exciting it to the S(3D]) state by the UV laser light and by detecting die laser-induced fluorescence emitted from S(3D]). Since only the fluorescence from the S fragments produced in the central region of the free-jet expansion was collected, the photoabsorption of ultracold (-5 K) OCS was selectively detected. 

The dimeric species M2(CO)i 0 can be considered to be special cases of the LM(CO)s class of compounds. In the solid phase Mn2(CO)IO is known to adopt the staggered conformation (94). Two M(CO)s fragments can thus be combined in Dtd symmetry to afford the MOs of the dimer as indicated below ... 

A variety of routes have been employed for the synthesis of hetero-metallic clusters containing Fe(NO)S fragments, and examples of such systems have been described in which the second metal is V, Mo, Co, Ni, and Pt it seems probable, given the variety of potential synthetic approaches to such mixed metal systems, that many more examples await discovery. 

The various mechanisms reported in the literature for these processes will now be reviewed. Some schemes (50) assume initiation in which the initiator s fragments are incorporated into the polymer, e. g.,... 

Such mechanisms might be questioned since in a recent work Goodman and Arnon (55) demonstrated the absence of initiator s fragments in the resulting polymer. In the course of their studies, polymerisation of y-benzyl-i.-glutamate was initiated in dioxane by 9-fluorenyl potassium or by radio-active sodium methoxide. The polymer produced by the former initiator was precipitated and examined spectrophotometrically. For Mjl ratio of 60 its degree of polymerisation was found from its intrinsic viscosity, to be about 180 and its solution did not absorb at A = 300 mfi where a strong absorption band (e = 104) of the fluorenyl moiety should appear. On the other hand, all the fluorenyl residues were found in the solution left after precipitation of the polymer. 

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