3-Sinensal synthesis

Among the acyclic terpene aldehydes, citral and citronellal hold key positions as fragrance and flavor chemicals, as well as starting materials for the synthesis of other terpenoids. Hydroxydihydrocitronellal is one of the most important fragrance materials. Derivatives of these aldehydes, particularly the lower acetals, are also used as fragrance materials. Acyclic sesquiterpene aldehydes are not very important as such, but they contribute to the characteristic fragrance and aroma of essential oils, for example, in the case of a- and /3-sinensal in sweet orange oil. 

A synthesis of the fragrant terpenoid Sinensal [Scheme 2.51] is noteworthy for two reasons.1()6 First, the method used to prepare the diethyl acetal is a rare example of an acetal synthesis which takes place under basic conditions secondly, the hydrolysis of the acetal product was only achieved after considerable effort by reaction with aqueous oxalic add adsorbed on silica gel.109... 

This regio- and stereoselective reaction was used to obtain the triunsaturated ester 1 in a short synthesis of the sesquiterpene p-sinensal (2). 

BUchi has used Mander s approach as a key step in his synthesis of a-sinensal (212 Scheme 50), and Corey has applied the ylidic 3,2-rearrangement to the efficient preparation of 3-cyclopentenones. Thus, base treatment of the sulfonium salt (213) first gave the rearranged product (215). Thermal vinylcyclo-propane ring expansion then produced the spiro compound (216). Deprotection finally gave the noncon-jugated cyclopentenone (217 Scheme 51). 

The reagent was also used3 for the synthesis of /3-sinensal (5), a flavor constituent of... 

When l-acyl-l-bromo-2-ethoxycyclopropanes 34 were treated with boron trifluoride-diethyl ether complex or a catalytic amount of acetic acid, / -bromo-y-oxo acetals 35 were obtained in good yield.This type of reaction has been applied in the synthesis of natural products such as juvenile hormone (JH-II), )8-sinensal and jasmonoids. ... 

The stereoselective synthesis of p-sinensal (14) has been achieved by reaction of the T -allylnickel(n) complex (12) (derived from bromomyrcene) with the chloro-... 

The aim of this book is to show you how this planning is done to help you learn the disconnection or synthon approach to organic synthesis. This approach is analytical we start with the molecule we want to make the target molecule) and break it down by a series of disconnections into possible starting materials. In the last chapter of the book we shall discuss the synthesis of the natural product a-sinensal (1) and we shall devise a route using five different, easily available starting materials (2-7). 

Hydroxy-frani-nerolidol (472a) is an important precursor in the synthesis of interesting avor of a-sinensal. Hrdlicka et al. (2004) reported the biotransformation of trans- (469) and CM-nerolidol (462) and cis-/trans-mixture of nerolidol using repeated batch culture of A. niger grown in... 

Addition of a Funtionalized Isoprene Unit to an Allyl Alcohol. I. The Synthesis of P-Sinensal and Related Topics. J. Amer. Chem. Soc. 91, 3281 (1969). 

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