Biomimetic, synthesis

J.E. Baldwin (1975, 1976A) has developed a biomimetic synthesis which is loosely analogous to the biosynthetic pathway which starts with the so-called Amstein tripeptide. Baldwin used bicyclic dipeptides more suitable for stereoselective in vitro syntheses. 

Biomimetic synthesis of natural nonfused polycyclic ethers by metal oxide-induced. syn-oxidative polycyclizations of hydropolyenes 98PAC355. 

The Mannich reactions plays an important role in pharmaceutical chemistry. Many /3-aminoalcohols show pharmacological activity. The Mannich reaction can take place under physiological conditions (with respect to pH, temperature, aqueous solution), and therefore can be used in a biomimetic synthesis e.g. in the synthesis of alkaloids. 

The elegant biomimetic synthesis of carpanone by Chapman and coworkers commences with the base-induced isomerization of 2-allyl-4,5-methylenedioxyphenol (4)3 to 2-(/ran.y-l-propenyl)-4,5-methylenedioxyphenol (3) (see Scheme 2). Compound 3, as simple as it is, is actually the key intermediate in this synthesis oxidative dimerization of 3 could result in the formation of carpanone (1) through the intermediacy of the C2-symmetric and highly reactive bis(quinodimethide) 2. 

The tetramerization of suitable monopyrroles is one of the simplest and most effective approaches to prepare porphyrins (see Section 1.1.1.1.). This approach, which is best carried out with a-(hydroxymethyl)- or ot-(aminomethyl)pyrroles, can be designated as a biomimetic synthesis because nature also uses the x-(aminomethyl)pyrrole porphobilinogen to produce uroporphyrinogen III. the key intermediate in the biosynthesis of all kinds of naturally occurring porphyrins, hydroporphyrins and corrins. The only restriction of this tetramerization method is the fact that tnonopyrroles with different -substituents form a mixture of four constitutionally isomeric porphyrins named as porphyrins I, II, III, and IV. In the porphyrin biosynthesis starting from porphobilinogen, which has an acetic acid and a propionic acid side chain in the y6-positions, this tetramerization is enzymatically controlled so that only the type III constitutional isomer is formed. 

Scheme 54 Sequential RCM and TADA reactions in Deslongchamps biomimetic synthesis of anhydrochatancin 271 [124]...

Cha JN, Stucky GD, Morse DE, Deming TJ (2000) Biomimetic synthesis of ordered silica structures mediated by block copolypeptides. Nature 403 289-292... 

The oxidation of triclosan was initiated by oxidation to the PhO radical. In analogy with reactions established in biomimetic synthesis, this nnderwent coupling to produce biphenyl ethers and biphenyls that were oxidized further to diphenoquinones (Zhang and Huang 2003). 

A biomimetic synthesis of (-)-xestospongin A (116), (+)-araguspongine B (129), and (+)-xestospongin C (130) was developed (Scheme 12) [43], starting from a Weiler s alkylation of ethyl acetoacetate (131) with 1-bromo-4-chlorobutane (132) to give the ethyl ester of 8-chloro-3-oxooctanoate... 

Mannich reactions, or a mechanistic analog, are important in the biosynthesis of many nitrogen-containing natural products. As a result, the Mannich reaction has played an important role in the synthesis of such compounds, especially in syntheses patterned after the biosynthesis, i.e., biomimetic synthesis. The earliest example of the use of the Mannich reaction in this way was Sir Robert Robinson s successful synthesis of tropinone, a derivative of the alkaloid tropine, in 1917. 

Another elegant example of the thermal generation and subsequent intramolecular cycloaddition of an o-QM can be found in Snider s biomimetic synthesis of the tetracyclic core of bisabosquals.2 Treatment of the starting material with acid causes the MOM ethers to cleave from the phenol core (Fig. 4.3). Under thermal conditions, a proton transfer ensues from one of the phenols to its neighboring benzylic alcohol residue. Upon expulsion of water, an o-QM forms. The E or Z geometry of the o-QM intermediate and its propensity toward interception by formaldehyde, water, or itself, again prove inconsequential as the outcome is decided by the relative thermodynamic stabilities among accessible products. 

Zanarotti, A. Synthesis and reactivity of lignin model quinone methides. Biomimetic synthesis of 8.0.4 neolignans. J. Chem. Res., Synop. 1983, 306-307. 

The absolute configuration of koumine has also been confirmed by a biomimetic synthesis of koumine from vobasine (50) (43). The configuration was correlated with L(—)-tryptophan, since vobasine was reduced to drega-mine (51) and the latter had been synthesized from L(—)-tryptophan with conservation of the (S) configuration of the amino acid, which corresponds to C-5 of koumine (44). 

A biomimetic synthesis of benzo[c]phenanthridine alkaloids from a protoberberine via the equivalent of a hypothetical aldehyde enamine intermediate has been developed (130,131). The enamide 230 derived from berberine (15) was subjected to hydroboration-oxidation to give alcohol 231, oxidation of which with pyridinium chlorochromate afforded directly oxyche-lerythrine (232) instead of the expected aldehyde enamide 233. However, the formation of oxychelerythrine can be rationalized in terms of the intermediacy of 233 as shown in Scheme 41. An alternative and more efficient... 

Scheme 41. Biomimetic synthesis of chelerythrine (205) and fagaridine (238) via the enamide aldehyde. Reagents a, B2H6 b, H202, NaOH c, PCC d, T1(N03)3, MeOH e, HC1 f, LAH g, MeOH h, NaBH4 i, p-TsOH, toluene j, I2, EtOH.

Scheme 42. Biomimetic synthesis of nitidine (243), fagaronine (244), and oxyterihanine (242) via enamide aldehydes.

Scheme 44. Biomimetic synthesis of corynoline (254), 11-epicorynoline (257), and their analog via enamine aldehydes. Reagents a, LAH b, Me2SC>4. c, KOH d, T1(N03)3, MeOH e, NaBH4 f, HC1 g, NaBH3CN.

The domino approach is also used by Nature for the synthesis of several alkaloids, the most prominent example being the biosynthesis of tropinone (0-16). In this case, a biomimetic synthesis was developed before the biosynthesis had been disclosed. Shortly after the publication of a more than 20-step synthesis of tropinone by Willstatter [14], Robinson [15] described a domino process (which was later improved by Schopf [16]) using succinaldehyde (0-13), methylamine (0-14) and acetonedicarboxylic acid (0-15) to give tropinone (0-16) in excellent yield without isolating any intermediates (Scheme 0.5). 

Vassilikogiannakis and coworkers described a simple sequential process for the biomimetic synthesis of litseaverticillol B (4-159) which includes a cycloaddition of 4-158 and singlet oxygen to give 4-160, followed by ring opening to afford the hydro-genperoxide 4-161 (Scheme 4.34) [55]. Reduction of 4-161 led to the hemiacetal 4-162, which underwent an aldol reaction to afford 4-159. 

You, S.-L., Razavi, H. and Kelly, J.W. (2003) A biomimetic synthesis of thiazolines using hexaphenyl-oxodipho-sphonium trifluoromethanesulfonate. Angewandte Chemie (International Edition in English), 42, 83—85. 

As mentioned earlier, biological systems have developed optimized strategies to design materials with elaborate nanostructures [6]. A straightforward approach to obtaining nanoparticles with controlled size and organization should therefore rely on so-called biomimetic syntheses where one aims to reproduce in vitro the natural processes of biomineralization. In this context, a first possibility is to extract and analyze the biological (macro)-molecules that are involved in these processes and to use them as templates for the formation of the same materials. Such an approach has been widely developed for calcium carbonate biomimetic synthesis [13]. In the case of oxide nanomaterials, the most studied system so far is the silica shell formed by diatoms [14]. 

Mann, S., Archibald, D.D., Didymus, J. M., Douglas, T., Heywood, B.R., Meldrum, F.C. and Reeves, N.J. (1993) Crystallization at inorganic-organic interfaces-Biominerals and biomimetic synthesis. Science, 261, 1286-1292. 

Sewell, S.S. and Wright, D.W. (2006) Biomimetic synthesis of titanium dioxide utilizing the R5 peptide derived from Cylindrotheca fusiformis. 

Wong, K.K.W. and Mann, S. (1996) Biomimetic synthesis of cadmium sulfide-ferritin nanocomposites. Advanced Materials, 8, 928-932. 

Shchukin, D., Price, R. and Lvov, Y. (2005) Biomimetic synthesis of vaterite in the interior of clay nanotubules. Small (Nano, Micro), 1, 510-513. 

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