Stereocontrolled approach

The interesting structures of the Lasioderma compounds have been the subject of many syntheses, serving as models for stereocontrolled approaches. More recent syntheses of serricornin form two groups those using chiral auxiliaries (oxazolidinone [250],boronic esters [251],and SAMP/RAMP [252]) and those involving chemoenzymatic steps ([253-255]). 

An alternative stereocontrolled approach involves the use of em-dizinc reagents to generate the corresponding cyclopropylzinc species, which was then trapped with iodine... 

More recently, a stereocontrolled approach to the synthesis of allocolchicinoids was disclosed by Wulff and co-workers using a diastereoselective benzannulation of chromium carbene complexes, Fig. (16) [104,105],... 

Stereocontrolled approaches to natural C-nucleosides have been based upon Baeyer-Villiger ring opening of bridged oxygen heterocycles. Noyori et al. have successfully converted lactone (59) to pseudocytidine (60 Scheme 17). 

The molecular complexities of these architecturally novel alkaloids have prompted intense studies to elaborate new and efficient methods and strategies for the synthesis of these products. Hence, several stereocontrol approaches have been developed to successfully construct the azaspirocyclic core of pinnaic acids and halichlorine, providing access to the formal total synthesis and highly stereoselectivity of these molecules (Christie et al. 2004 Zhang et al. 2005 Andrade and Martin 2005 Clive et al. 2005 and references cited therein). In particular, Danishefsky s research group has reported the first total synthesis of halichlorine (Trauner et al. 1999), supporting the previous conclusions regarding the structure of this alkaloid (Kuramoto et al. 1996 Arimoto et al. 1998), and has... 

Alkylation of vinyl lactones. Trost and Klun have reported that alkylation of TT-allylpalladium complexes derived from vinyl lactones provides a stereocontrolled approach to acyclic systems such as the side chains of a -tocopherol and vitamin K. The alkylation of lactones 1-4 proceeds with greater than 95% stereoselectivity. 

Using 25 mol % of the more practical Ni(CO)3PPh3 catalyst under CO (1 atm, THF/MeOH 4 1, r.t.), exclusive monocyclization of iodoenyne (284a) -> (286a) was accomplished (Scheme 60 Table 18, entry 1). ° This unusual stereocontrolled approach to an exocyclic trisubstituted alkenic bond is consistent with a suprafacial allylnickel/alkyne insertion, (284 X = NiLn) (285). Malonate (284b X = I) yielded, under similar reaction conditions, monocyclized ester (286b 41%) and bicyclo[3.3.0]octenone... 

Nakahara Y, lijima H, Ogawa T (1994) Stereocontrolled approaches to 0-glycopeptide synthesis. In Kovac P (ed) Synthetic oligosaccharides. Indispensable probes for the life sciences. ACS Symposium Series 560. American Chemical Society, Washington, p 249... 

Paquet, F, Sinay, P, New stereocontrolled approach to 3-deoxy-D-manno-2-octulosonic acid containing disaccharides, J. Am. Chem. Soc., 106, 8313-8315, 1984. 

The amino acid derived carboxy group can be utilized as a functionality for further synthetic manipulations, e.g. for cyclization reactions to 1,3-bridged P-carbolines, using the Dieckmann reaction, a promising stereocontrolled approach to macroline-related alkaloids (Scheme 14). > ... 

Paquet, F., and Sinay, P, Intramolecular oximercuration-demercuration reaction. A new stereocontrolled approach to sialic acid containing disaccharides. Tetrahedron Lett., 25, 3071, 1984. 

The C14-C20 segment [108] Stereocontrolled formation of the C15 and chiral centers was the major problem encountered in the synthesis of this segment. A route starting from benzoate 165 [111] was selected after several attempts (Scheme 21). Standard chemical operations led to allylic alcohol 166. Stereocontrolled approach from the re-re face of the double bond in 166 was insured by a diborane-oxidative treatment of the bulky bis-boronate ester 167. 1,2-Diol protection, phenoxythiocarbonylation-hydride reduction [112], and deprotection led to diol 169, representing the C14-C20 segment. 

Trost, B. M., and T. R. Verhoeven New Synthetic Reactions. Catalytic vs. Stoichiometric Allylic Alkylation. Stereocontrolled Approach to Steroid Side Chain. J. Amer. Chem. Soc. 98, 630 (1976). 

An elegant stereocontrolled approach to ( )-vinyl sulphides proceeds via the cyclopropylalkene (255). By ring-opening of the cyclopropane, ( )-vinyl sulphides (256) are obtained with 100% specificity and in yields of 75—96%. Once... 

Liu X, Shimizu M, Hiyama T (2004) A Facile stereocontrolled approach to CF3-substituted triarylethenes synthesis of panomifene. Angew Chem Int Ed 43 879-882... 

Hanessian S, Claridge S, Johnstone S. The power of visual imagery in synthesis planning. Stereocontrolled approaches to CGP-60536B, a potent renin inhibitor J. Org. Chem. 2002 67 4261 274. 

Couladouros EA, Vidali VP. Novel stereocontrolled approach to syn- and awO -oxepene-cyclogeranyl trans-fused polycyclic systems asymmetric total synthesis of (—)-aplysistatin, (+)-palisadin A, (+)-palisadin B, (+)-12-hydroxy-palisadin B, and the AB ring system of adociasulfate-2 and toxicol A. Chem. Eur. J. 2004 10(15) 3822-3835. 

Mehta, G. and Murthy, A.N. (1987) A general stereocontrolled approach to the 5-8 fused ring system application to the total synthesis of marine natural product ( )-precapneUadiene. /. Org. Chem., 52, 2875-2881. 

Ghosh, S., Patra, D., and Samajdar, S., Intramolecular [2 +2 ]-photocyclo-addition-cyclobutane rearrangement. A novel stereocontrolled approach to highly substituted cyclopentanones. Tetrahedron Lett., 37, 2073, 1996. 

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