A reação de ciclização de prins: uma estratégia eficiente para síntese estereosseletiva de anéis tetraidropirânicos substituídos

Abstract

Recebido em 5/5/05; aceito em 27/9/05; publicado na web em 12/4/06 THE PRINS CYCLIZATION REACTION: AN EFFICIENT STRACTEGY FOR THE STEREOSELECTIVE SYNTHESIS OF SUBSTITUTED TETRAHYDROPYRAN RINGS. The Prins cyclization reaction has significantly advanced in the last years as demonstrated by a number of applications described in the literature. The objective of this report is to introduce this powerful synthetic methodology to the undergraduate and graduated student, since it is rarely presented in an organic synthesis formal course. This reaction is, in some cases, the methodology of choice for the preparation of natural products or drugs that present the tetrahydropyrane moiety in their structures. In this report we show some aspects of this reaction, including mechanism, scope and limitations.

Synthesis and Anticancer Activities of Novel Guanylhydrazone and Aminoguanidine Tetrahydropyran Derivatives

“…The oxidation of tetrahydropyran alcohols to the corresponding ketones 8a-c (step iii, Scheme 1) was performed in high yields by using PCC in dichloromethane as a solvent (95%-98% yields). The guanylhydrazone 2-4 ( Figure 1) were prepared in quantitative yields (100% yields) by reacting ketones 8a-c with aminoguanidine hydrochloride and ethanol as a solvent (no catalysts were used) promoted by 5 min of microwave It is important to note that compounds 2-7 are Meso compounds which greatly simplifies these syntheses, since only relative configuration (cisztrans) must be controlled [12].…”

“…Substituted tetrahydropyranyl moieties are extensively distributed in the natural products' structures that present a large pharmacological profile [12]. There are many synthetic methodologies to prepare this moiety, i.e., the Prins cyclization reaction and others.…”

“…Normal cell lines, L929 (murine fibroblast) cells and human peripheral blood cells (PBMC) were also evaluated. It is important to note that compounds 2-7 are Meso compounds which greatly simplifies these syntheses, since only relative configuration (cis\trans) must be controlled [12].…”

Synthesis of cis and trans 2,4,6-Tetrahydropyranols via Prins-Type Cyclization and Mitsunob Inversion

“…The Prins cyclization of the substituted homoallylic alcohols and aryl/aliphatic aldehydes are generally promoted by strong Brønsted or Lewis or protic acidic conditions is an old reaction [2,3] that is now emerging as an efficient method for the substituted tetrahydropyrans synthesis [4,5]. Oxygen hetero atoms can be captured at the 4-position of the tetrahydropyranols ring, although most acids lead to esters that must be hydrolyzed to form 4-hydroxy tetrahydropyranols products [6,7].…”

“…The majority Prins cyclizations use super stoichiometric acid to promote the reaction due to the acid counterion is trapped in the product, thus consuming the acid [3]. In general, 2,4,6-cis tetrahydropyranols all equatorial substituted are obtained in high diastereoselectivity [5]. Rychnovsky et al [8] developed the first axial-selective Prins cyclization method to the hetero atom at the 4-position, escalating the synthetic scope of this reaction.…”