Tetrahydro optically active

Just as selective oxidation can be carried out on these systems, reduction also occurs with considerable selectively. Hydrogenation of binaphthol (Pd catalyst) in glacial acetic acid at room temperature for seven days affords the octahydro (bis-tetrahydro) derivative in 92% yield with no apparent loss of optical activity when the reaction is conducted on optically pure material. The binaphthol may then be converted into the bis-binaphthyl crown in the usual fashion. 

The acetylation of isotripiperideine by means of a ketone in nonpolar media affords a compound which decomposes in acidic media to piperideine and a monoacety.l derivative of the enamine form of tetrahydro-anabasine (195). This monoacetyl derivative is identical with the alkaloid amodendrine (312). A similar acylation with cinnamoylchloride affords the alkaloid orensine (196) (313), the optically active form of which is the natural alkaloid adenocarpine (314). The hydrolysis of alkaloid santiaguine gives a-truxilic acid (314). 

The second system studied was the separation of the chiral epoxide enantiomers (la,2,7,7a-tetrahydro-3-methoxynaphth-(2,3b)-oxirane Sandoz Pharma) used as an intermediate in the enantioselective synthesis of optically active drugs. The SMB has been used to carry out this chiral separation [27, 34, 35]. The separation can be performed using microcrystalline cellulose triacetate as stationary phase with an average particle diameter greater than 45 )tm. The eluent used was pure methanol. A... 

The optically active 1,3-/ram-substitutcd tetrahydro-/f-carboline 3 is obtained predominantly on treatment of the imine 2, derived from L-tryptophan and isovaleraldehyde, with A-benzyl -oxycarbonyl-L-prolyl chloride145. 

The Enders method has also been used as a key step in the synthesis of optically active Ar-heterocycles. The use of cyclic 1,3-diketones for the preparation of the SAMP or RAMP lithium azaenolates is shown by the synthesis of substituted 4,6,7,8-tetrahydro-2,5(l//,3//)-quinolinediones 2. Michael addition of 1 with, for example, benzylidene propanedioates followed by removal of the auxiliary and lactamization gives 2 with > 98% ee201. 

Reaction of alkyl phenylmethanesulphinates 100 with n-butyllithium in tetrahydro-furan at — 80 °C afforded the corresponding benzyl n-butyl sulphoxide160 (equation 53). Preparation of optically active sulphoxides by this reaction will be discussed later in this chapter. 

An asymmetric synthesis of 1-aryltetrahydroisoquinolines 79 from chiral amide 78 was reported <96TL(37)4369>. Optically active cis- or rranj-1,3-disubstituted tetrahydro-isoquinolines can he prepared hy a modification of this procedure. 

Organocatalytic annulation of phthalazinium iodide 51 in the presence of (2A,5A)-2,5-dibenzylpyrrolidine furnished optically active (l,9,llM)-tetrahydro-l//-pyrido[2,l-tf]phthalazine 52 with high diastereo- and enantioselectivities (Equation 8) <2005AGE6058>. 

There has been no report on this kind of compound in the literature for the period concerned. The perhydro derivatives were, on the contrary, well-studied for several years and applied in a variety of routes for the total synthesis of natural products or to produce optically active derivatives, mainly following the Meyers protocol <1984JA1146>. Only two examples of dihydropyrrolo[2,l- ]oxazoles are available and one example of a tetrahydro derivative is described. 

In all cases, mixtures of cis and trans diastereoisomers are reported. In terms of experimental observation, it is now possible to prepare 1,3-disubstituted tetrahydro-j8-carbolines and 1-substituted tetrahydro-/3-carbolines of known absolute stereochemistry. For example, if optically active A -benzyltryptophan methyl ester of known chirality reacts with aldehydes in refluxing benzene, the trans derivative is obtained. Arylglycidate was also used in the synthesis instead of aldehydes (78CPB2305). 

The protoberberine alkaloid, xylopinine, has been synthesized in an optically active form by Kametani et al.22 ). A key reaction in this synthesis was the photochemical cyclization of the optically active amino acid derivative 1,2,3,4-tetrahydro-6,7-dimethoxy-3-methoxycarbonyl-1 -methylene-2-veratroylisoquinoline with 1,3... 

The conformations of the 2-oxo-tetrahydro-l,3-oxazines obtained from phosgene and the isomeric 3-amino-2,3-diphenylpropanols were used by Fodor et al. as an ingenious criterion for the configurational determination of the aminopropanols.13,14 The erythro form yielded an oxazinone that showed optical activity 4-8 times stronger than that from the threo form. 

Panek et al. employed the optically active amines 252 and 254 [57]. Their condensation with various aldehydes in the presence of MgS04 probably afforded the corresponding imines, which were treated with TiCl4. The resulting substituted 1,2,5,6-tetrahydro pyridines were finally protected, affording the corresponding tri-fluoroacetamides 253 and 255. In all cases, the desired tetrahydropyridines 253 and 255 could be isolated in excellent yields. The IMSC condensation also displays a high diastereoselectivity (Scheme 13.93). 

The (S)-(-)-proline catalyzed asyimietric aldol cyclization of the triketone to the optically active bicyclic aldol product, followed by dehydration to the optically active enedione, (+)-(7aS)-2,3,7,7a-tetrahydro-7a-methyl-lH-indene-l,5(6H)-dione, has been described, and two alternative reaction mechanisms have been suggested by the submitters. The exact... 

Up to the present the only method used for the reduction of 0-naphthylamine for obtaining the tetrahydro base has been with sodium and alcohol. This method was first described by Bamberger and Muller.2 It is possible to substitute ethyl alcohol for amyl alcohol but the yield is distinctly lower. The base has been resolved into its optically active components.3... 

The Pictet-Spengler cyclization proceeds in vitro as in Fig. 2, which shows a hypothetical example in the isoquinoline series, via several distinct intermediates which cannot be isolated in the laboratory (6c, I Ob). Addition of acetaldehyde to a phenethylamine activated by a phenolic hydroxy group first affords a carbinolamine, which, under the influence of acid, dehydrates to a Schiff base that is most likely present as the more stable E isomer, affording on protonation directly the racemic tetrahydro-isoquinoline [( )-TIQ] (I0a,b). In attempting to explain the formation of optically active mammalian isoquinolines in vivo, we cannot disregard the possibility that the phenolic group of the phenethylamine substituent is... 

Tetrahydro-)8-carbolines substituted at C-1 by a methyl group occur in mammalian tissues and fluids as optical isomers, and they are often present in unequal proportions of the enantiomers (29,30). There are now several practical methods available to prepare optically active TBC, as summarized in Fig. 8. 

Tetrahydro-/3-carboline (IS,3S)-dicarboxylic acid, 127-128 Tetrahydro-/3-carbolines optically active, 126-128 reaction, 125-126... 

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