Cis-Enediol

Thr90 sam 268 Base catalyzed cis-enediol formation by HjO interaction b-439 e=421... 

Support for this path comes from the reaction between Cpf Zr(CO)2 and Cpf ZrH2, which forms a cis-enediolate. 

Lanthanide hydrides of type CpfSmH are capable of both reducing and coupling carbon monoxide (Scheme 38) [282]. The initially formed cis enediolate isomerizes to trans-[Cp Sm(Ph3pO)]2(jt-OCH=CHO) at ambient temperature in hours to days depending on sample concentration. The Sm-O bond of the bridging enediolate moiety is in the range of terminal Sm-0(alkoxide, enolate) bonds (Table 18). 

Figure 6.3 Generation and fate of the (probably cis) enediolate from dihydroxyace-tone and glyceraldehyde phosphates.

Figure 1. The Isomerization of a ketone to an aldehyde. The reaction in aqueous solution is base-catalysed and is thought to proceed through a cis-enediol intermediate.

Elegant isotope labelling studies by Rose and coworkers (Rieder and Rose, 1959 Rose, 1962) established the general mechanistic features of the TIM reaction. Proton transfer is mediated by a single enzymatic base, and the reaction proceeds via an intermediate that is either a cis enediol phosphate (Figure 2) or one of the tvo possible symmetrical enediolates. The evidence for enzyme-mediated proton transfer is the catalysis by the enzyme of loss of radioactive label from substrate to solvent water, or of exchange-in of label from deuterated or tritiated water to... 

Kozarich and Chari suggest that the enzymic reaction most likely involves a cis-enediol intermediate, on the basis of two observations. First, the enzyme has the surprising ability to catalyze the stereospecific conversion of the thiohemiacetal (11), formed from (glutathiomethyl)glyoxal (10) and j8-mercaptoethanoI, to the thioester 12, established to have the (8)-configuration at C-2 on the basis of chemical degradation to L-lactate (111) [Eq. (24)] ... 

The proton which has been removed from C-2 to form the cis-enediol is conserved (7, 30, 31, 32) and transferred to C-1 from the same side of the double bond to form D-xylulose of the proper stereochemistry (32). 

D glucose Trans enediol D fructose Cis enediol D mannose... 

Synthesis of a potential Src homology-2 (SH2) domain inhibitor R,R,R)-(45) incorporating a 1,4-cis-enediol scaffold has been reported by Borch et al. Key steps included stereocontrolled syn-a do coupling, amide alky-nylation, and asymmetric ketone reduction. ... 

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