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A simple, inexpensive and efficient method for the selective cleavage of N-Boc protecting group under acidic conditions on high load Wang resin is described. This method employs the use of concd sulfuric acid in 1,4-dioxan and provides an efficient process for the complete Boc deprotection with minimal loss of substrate through cleavage from resin. Solid phase organic synthesis (SPOS) has been widely applied for preparing small organic molecule libraries for screening purposes. 1 More recently, the scale-up of a variety of solid phase syntheses using a high load (4 mmol/ g) Merrifield resin has been reported. 2 Consequently, the approach of using high load resins in solid phase chemistry for the preparation of the initial quantities of drug substance required for pre-clinical toxicological studies is now feasible. This not only requires that all steps are chemically efficient (conversion and isolated yield) but also imposes cost limitations on the use of certain reagents.In general, the use of N-Boc protection strategies for solid phase synthesis is currently limited to acid stable resins with the initial step in the synthesis being the direct attachment of substrate to Merrifield resin. However, the forcing conditions required to cleave the product from the resin limits the nature of compounds that can be prepared using this strategy. The alternative approach is to use orthogonal base sensitive protecting groups such as Fmoc in association with modified resins such as Wang and 2-chlorotrityl, which allow the use of milder resin cleavage conditions such as 50% TFA in dichloromethane (DCM). 3,4 However, on larger scales the cost associated with the use of Fmoc protected monomers can become prohibitive. In this letter we describe a simple method of N-Boc deprotection, which is compatible with Wang resin.Recently we wished to prepare the dipeptide (4) and opted to follow a SPOS strategy using high load Merrifield derived Wang resin, Scheme 1. Although there are a number of methods available for N-Boc deprotection on solid support, 5 including the use of TMSOTf/Lutidine, 6 TMSCl/ Phenol, 7 , silicon tetrachloride, 8,9 aluminium chloride 10 and dilute aqueous HCl in organic solvents, 11,12 we encountered difficulties in the selective removal of a N-Boc group without appreciable loss of substrate through cleavage from the resin. For example, using TMSOTf/2,6-lutidine, at least two treatments with fresh reagents were necessary and even then the reaction was incomplete giving rise to other unidentified impurities. Similarly, whilst the use of TMSCl/Phenol for the selective removal of the Boc protection appeared to work well on small scale (1-5g), the results were inconsistent and at times gave as much as 20-25% loss of product from cleavage of the resin. Attempts to enhance this protocol through the use of fresh TMSCl (to minimise the presence of residual HCl) or TMSCl pre-treated with sodium carbonate and high purity phenol (>99%) failed to give more consistent results. Furthermore, attempts to increase selectivity by u...

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Previous literature has demonstrated that peer support is instrumental for the promotion of adaptive academic and mental health outcomes; however, limited research has examined prospective directional associations between peer support and adjustment within college settings. The purpose of this study was to investigate the longitudinal associations between peer support, academic competence, and anxiety among U.S. college students. U.S. students from a diverse 4-year university ( N = 251, 75% women, 24% men, and < 1% a different gender) reported on peer support, academic competence, and anxiety using validated questionnaires at two time points (Fall term of sophomore year and Spring term of senior year). Results showed that peer support was positively associated with academic competence over time but was not significantly related to future anxiety. Academic competence did not significantly predict peer support or anxiety over time, but anxiety was associated with lower future academic competence. These findings offer insight into how types of social relationships link with academic motivation and anxiety over time within educational settings.