Baldwin group

In fact the results are not quite as dramatically different as they appear when presented this way. The mechanistic rate constants are derived from phenomenological rate constants that can be described as linear combinations of the mechanistic ones. The discrepancy between the two results can be traced to a difference in just one of the phenomenological rate constants—the one corresponding to the first order loss of optical activity for a 1 1 mixture of (1R,25)- and (lR,2R)-phenylcyclopropane-2-d. The peculiar feature of this problem is that the Berson group obtained an internally consistent set of results from two independent experiments with one value for this rate constant and the Baldwin group also obtained an internally consistent set from two independent experiments but with a value that differed by a factor of 2.7 from that found by the Berson group. It is hard to know how to reconcile such results and so, to be objective, one must probably say that despite the immense amount of effort put into the problem the mechanism of stereomutation of phenylcyclopropane remains something of a mystery. 

The Bohlmann-Rahtz synthesis is viable for the construction of di- or tri-substituted pyridines and has been applied in the synthesis of complex target molecules. The Baldwin group was one of the first to employ this method for the construction of pyridine substituted a-amino acids. Exposure of alkynyl ketone 182 to 3-aminocrotoyl ester 183 or ketone 184 in ethanol at reflux gave rise to the desired pyridyl-P-alanines 185 and 186, respectively, which were subsequently deprotected to afford the a-amino acid L-azatyrosine analogues 187 and 188, respectively. 

In all cases examined the ( )-isomers of the allylic alcohols reacted satisfactorily in the asymmetric epoxidation step, whereas the epoxidations of the (Z)-isomers were intolerably slow or nonstereoselective. The eryfhro-isomers obtained from the ( )-allylic alcohols may, however, be epimerized in 95% yield to the more stable tlireo-isomers by treatment of the acetonides with potassium carbonate (6a). The competitive -elimination is suppressed by the acetonide protecting group because it maintains orthogonality between the enolate 7i-system and the 8-alkoxy group (cf the Baldwin rules, p. 316). 

The palladium-catalyzed cyclization of compound 138 amply demonstrates the utility of the Stille reaction as a macrocyclization method (see Scheme 37). This efficient ring closure is just one of many examples disclosed by J.E. Baldwin and his group at Oxford.58 Interestingly, compound 138 can be employed as a stereoisomeric mixture of vinylstannanes because both stereoisomers converge on the same cyclized product. To rationalize this result, it was suggested that the configuration of the vinylstannane moiety is conserved in the cyclization, but that the macrocycle resulting from the (Z)-vinylstannane stereoisomer isomerizes to the thermodynamically favored trans product under the reaction condi-... 

A. C. Baldwin, in TheChemistryofFurwtional Groups, Peroxides Ed.S. Patai), Wiley, New York, 1983. 

Chatterjee and Robinson ° studied the nitration of m-nitrophenyl benzyl sulfone, which occurred exclusively in the benzyl ring producing 25% ortho, 28% meta and 47% para isomer. Baldwin and Robinson " nitrated a series of phenyl alkyl sulfones PhSOjR. When R = Me, 98.5% of meta derivative was found but the amount of meta isomer fell with the chain length and branching of the alkyl group, e.g. n-Bu, 85.7% i-Pr, 80.0%. This was attributed to the electron repulsive influence of the higher alkyl groups. 

Avgelj, F., Luo, P., and Baldwin, R. L. (2000). Energetics of the interaction between water and the helical peptide group and its role in determining helix propensities. Proc. Natl. Acad. Sci. USA97, 10786-10791. 

We saw at the outset of this section that for sulfenic anhydrides the thiolsulfinate structure RS(0)SR was thermodynamically preferred over RSOSR. Perhaps it is therefore fitting to close it by mentioning a situation in which another isomeric structure, that of a thiosulfoxylate ROSSR, has been found to be preferred over thiolsulfinate. Baldwin et al. (1971) reported that the thiolsulfinate [21] isomerizes readily to thiosulfoxylate [22] (76). On the other hand, in the system lacking the methyl groups, [23]—[24], thiolsulfinate [231... 

Calabrese, E.J. and L.A. Baldwin. 2002. Hormesis and high-risk groups. Regul. Toxicol. Pharmacol. 35 414- 28. 

We began our calculations of the PES for the ring opening of cyclopropane in an attempt to resolve an apparent conflict between the results of experiments by Berson and co-workers and by Baldwin and co-workers. However, graduate students in our research group were among the experimentalists whose research ultimately benefited the most from the predictions made by our calculations. 

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