Synthesis of segment

Synthesis of Segmented Siloxane-Ester Copolymers with (Si—O—C) Linkages 1851... 

Epimerization of alpha-configuration of 10 into a p-equatorial configuration through acidic treatment and decomplexation by iodine provided the pseudo enantiomeric form of D-glucose derivative 11 (5). Finally, 11 is converted into the hetero olefin 12 which then received a variety of nucleophiles by chelation control to accomplish the synthesis of segment C of TTM 13. 

Scheme 10. Synthesis of segmented copolymers via amic ester precursors [53]...

In this chapter, synthesis of segmented copolymers and the thermodynamics of phase separation will be discussed briefly. The main focus, however, summarizes recent research activities in the study of structure-property relationships of these segmented copolymers. 

A similar convergent synthetic strategy was applied in our synthesis of annona-cin, using sequential assembly of the three key fragments, aldehyde 29, phospho-nium 30, and alkyne 14 (Scheme 10-9). In this synthesis, the a,p-unsaturated-y-lactone unit was constructed after completion of the linear skeleton. A modified method was applied into the synthesis of segment 3 (Scheme 10-5), in which the six carbons, as well as two chiral centers from D-glucono-8-lactone, were all incorporated into the final target. Therefore, the efficiency of the whole... 

This chapter discusses the complete synthesis of Segment B (5 steps), the final part of the synthesis of Segment C (6 of 9 steps), their combination to building block BC (3 steps), the introduction of Segment A and the completion of the total synthesis of ZK-EPO (1). The synthesis of Segment A (11 steps) is not discussed. 

The formation of ketone 7 completes the synthesis of Segment B in an overall yield of 47 % starting from 3. In the following the synthesis of the Segment C is discussed. 

The longest linear sequence involves 22 steps and includes the construction of Segment C, its combination with Segment B, the introduction of Segment A, and the completion of the target compound. This chapter discusses 19 of these steps. The published synthesis of Segment C starts with 4-chloro-3-nitro-benzoic acid 22. The overall yield for this linear sequence is 0.9 %. 

The synthesis of Segment A was published earlier and is not included in this chapter. ... 

When synthesis of segment C begins, which other segment is also being synthesized ... 

The synthesis of segment C.77-C.115 from segments C.77-C.84 and C.85-C.115 involved the liberation of an aldehyde at C.85 from its protected form as a dithioac-etal, RCH(SEt)2, by mild oxidative deblocking (H/NaHCOs, acetone, water) and the use of the p-methoxyphenyldiphenylmethyl (MMTr) group to protect the hydroxyl group at C.77. The C.77 MMTr ether was subsequently converted to a primary alcohol (PPTS/MeOH-CH2Cl2, rt) without affecting the 19 t-butyldimethylsilyl (TBS) ethers or the cyclic acetonide at C.lOO-C.lOl. 

Syntheses of Three Optically Active Segments 3-2-1. Synthesis of Segment A... 

Composition limitation associated with the random copolymer approach and process complexity, and fair-to-inadequate reproducibility encountered in the two-step synthesis of segmented glycolide copolymer, provided tire incentive to explore a simple yet reliable approach to prepare crystalline glycolide copolymers with a broad range of physicochemical properties and possibly unique functional performance/ ... 

FIGURE 8.6 Synthesis of segmented poly(ester amidejs derived from bisamide-diols, dimethyl adipate, and 1,4-butanediol based on Ref. [35]. 

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