Pivaloyl acylating agents

Selective acylation of a primary alcohol in the presence of one or more secondary alcohols is easily achieved with hindered acylating agents such as pivaloyl chloride [Scheme 4.326],604 A more extensive discussion of the methods for... 

Yamada and Ohe [38] reported the resolution of secondary alcohols by axially chiral twisted amides. (S)-4-Alkyl-3-pivaloyl-l,3-thiazoHdine-2-thiones 4 and the oxazolidine analogue 5, readily prepared from the corresponding i-amino alcohols, were used as acylating agents for secondary alcohols (5 equiv). The corresponding pivalates were obtained in 26-84% ee. 

Bufotenine has been found to be behaviorally inactive, or only weakly active, in most animal studies, although at 15 mg/kg, it did produce the head-twitch resonse in mice (43). It was also behaviorally active in experiments in which the blood-brain barrier was bypassed (78). Acylation of the polar hydroxy group of bufotenine increases its lipid solubility (65,74) and apparently enhances its ability to cross the blood-brain barrier (64). For example, O-acetylbufotenine (5-acetoxy-N,N-dimethyltryptamine 54) disrupted conditioned avoidance behavior in rodents (65) and produced tremorigenic activity similar to that elicited by DMT (37) or 5-OMeDMT (59) when administered to mice (64). In this latter study, a comparison of brain levels of bufotenine after administration of O-acetylbufotenine with those of DMT and 5-OMeDMT revealed bufotenine to be the most active of the three agents, based on brain concentration. The pivaloyl ester of bufotenine also appears to possess behavioral activity, since stimulus generalization was observed when this agent was administered to animals trained to discriminate 5-OMeDMT from saline (74). 

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