RESUMO
The stereoselective synthesis of sialic acid glycoconjugates is still a challenge in the field. Surprisingly, little is known on the regioselective O-substitution of sialic acids. Consequently, the effect of O-protecting groups and/or regioselectively protected building blocks in sialylations, remains practically unexplored. O-Picoloyl protecting groups have emerged as novel substituents that have a profound effect on sialylations. Recently, high stereoselectivities were obtained by introducing picoloyl groups at the C-4 and C-7/C-8 positions. However, to understand the relationship between the position of the picoloyl group and its exact effect in sialylations, a convenient access to a wider range of regioselectively picoloylated building blocks is needed. Reported herein is a new method that provides an accessible route to a wide array of regioselectively acylated building blocks. The regioselective introduction of picoloyl groups at various O-positions was achieved either by controlled direct picoloylation or by applying a modified ReSET methodology.
RESUMO
BACKGROUND: Many of the symptoms, consequences, and risk factors for frailty are shared with late-life depression. However, thus far, few studies have addressed the conceptual and empirical interrelationships between these conditions. This review synthesizes existing studies that examined depression and frailty among older adults and provides suggestions for future research. METHODS: A search was conducted using PubMed for publications through 2010. Reviewers assessed the eligibility of each report and abstracted information on study design, sample characteristics, and key findings, including how depression and frailty were conceptualized and treated in the analysis. RESULTS: Of 133 abstracted articles, 39 full-text publications met inclusion criteria. Overall, both cross-sectional (n = 16) and cohort studies (n = 23) indicate that frailty, its components, and functional impairment are risk factors for depression. Although cross-sectional studies indicate a positive association between depression and frailty, findings from cohort studies are less consistent. The majority of studies included only women and non-Hispanic Whites. None used diagnostic measures of depression or considered antidepressant use in the design or analysis of the studies. CONCLUSIONS: A number of empirical studies support for a bidirectional association between depression and frailty in later life. Extant studies have not adequately examined this relationship among men or racial/ethnic minorities, nor has the potential role of antidepressant medications been explored. An interdisciplinary approach to the study of geriatric syndromes such as late-life depression and frailty may promote cross-fertilization of ideas leading to novel conceptualization of intervention strategies to promote health and functioning in later life.
