Achla Trehan

All-cis-retinal and 7-cis,9-cis,11-cis-retinal1

Abstract A modified 15 + 5 route led to 7- cis ,9- cis ,11- cis -retinonitrile in high selectivity and also a lesser amount of all- cis -retinonitrile. DIBAL reduction gave the corresponding retinal isomers. The absorption maximum 287nm of all- cis -retinal reveals the distorted nature of the chromophore.

The doubly hindered 7,11-dicis, 7,9,11-tricis, 7,11,13-tricis and all-cis isomers of retinonitrile and retinal☆

Abstract Reaction of a modified C-5 phosphonate with 7-cis-C15-aldehyde provided the doubly hindered 7-cis,11-cis-retinal and a smaller amount of the hitherto unknown 7-cis,11-cis,l3-cis-retinal which readily rearranged to the 7,13-dicis isomer. Properties of these and the 7,9,11-tricis and the all-cis isomers are reported. Molecular mechanics calculation was used to verify possible application of the proposed consecutive 6e electrocyclization mechanism for rearrangement of 7-cis,11-cis,13-cis- and all-cis-retinals. v#51b11p3768b

On retention of chromophore configuration of rhodopsin isomers derived from three dicis retinal isomers

Abstract By the chromophore extraction-HPLC method, it has been shown that an isomeric mixture of pigments (9,11- dicis , 9- cis , and 9,13- dicis ) was formed from interaction of 9- cis , 11- cis -retinal with bovine opsin. That from 7- cis ,9- cis -retinal retained the original geometry and that from 7,13- dicis contained almost completely the isomerized 7- cis pigment.

FT-IR spectra of all sixteen isomers of retinal, their isolation, and other spectroscopic properties.

Abstract The FT-IR spectra of all sixteen isomers of retinal, their synthesis completed only recently, are reported. Characteristic trends of the polycis isomers (in C,C, double bond, single bond and HOOP band regions) are discussed and compared with those of the mono-cis isomers. The 7-cis and 7,9-dicis isomers of three deuterioretinals (7D, 19,19,19,-D3, and 8,19,19,19-D4) have been prepared, confirming some of vibrational assignments. Conditions for purification of these isomers and other spectroscopic properties (1H-NMR, UV/VIS) are also provided.

Isomers, visual pigment, and bacteriorhodopsin analogs of 3,7,13-trimethyl-10-isopropyl-2,4,6,8,10-tetradecapentaenal and 3,7,11-trimethyl-10-isopropyl-2,4,6,8,10-dodecapentaenal (two ring open retinal analogs)☆

Abstract Six geometric isomers of 2 (3,7,13-trimethyl-10-isopropyl-2,4,6,8,10-tetradecapentaenal) have been isolated and characterized. Of these, four (equivalent to 9- cis , 11- cis , 5,9- dicis , and 5,11- dicis of retinoids) were found to form stable visual pigment analogs. So were four isomers (equivalent to 7- cis , 9- cis , 11- cis , and 9,13- dicis ) of 3 (3,7,11-trimethyl-10-isopropyl-2,4,6,8,10-dodecapentaenal). These analogs suggest that the hydrophobic pocket is more flexible than what was recognized earlier, perhaps capable of accepting analogs with 6- S-trans as well as a 6- S-cis conformers. The presence of bacteriorhodopsin analogs from isomers of 2 was also reported.

Recent Advances in the Synthesis of Retinoids and Visual Pigment Analogs Studies

Recent activities in the field of synthetic retinoids have been stimulated by analog studies in the areas of cancer prevention using vitamin A and its derivatives,1 visual pigments2 and bacteriorhodopsin3 and other retinal containing proteins.4 It will not be possible to review here the variety of compounds available in the literature. Nor, will it be wise to repeat the effort of others who have already produced several extensive review articles.5 Instead, in this paper only efforts directed toward preparation of stereoisomers of vitamin A, a topic of interest here will be summarized.