Asymmetric synthese of de-ABC-cholestan-14-one and de-AB-cholest-8-en-9-one by an extracyclic methodology

Synthesis of a Vitamin D3Hydrindan Ring−Side-Chain Building Block, Involving Tandem Conjugate Addition and Alkylation Reactions

“…The residue was chromatographed on SiO 2 (30 g, 3% EtOAc in hexane) to give 4 (335 mg, 64%): IR (film) 1672, 1639 cm -1 ; 1 H NMR (200 MHz) δ 5.72 (1H, br s), 2.75−0.75 (17H, m), 1.07 (3H, s), 0.95 (3H, d, J = 6.4 Hz), 0.86 (6H, d, J = 6.6 Hz); 13 C NMR and DEPT (50 MHz) δ 199.19 (0), 180.05 (0), 121.35 (1), 55.75 (1), 44.99 (0), 39.39 (2), 37.03 (2), 35.74 (2), 34.34 (1), 33.52 (2), 28.86 (2), 27.97 (1), 26.77 (2), 23.67 (2), 22.76 (3), 22.52 (3), 18.71 (3), 16.14 (3); MS EI 262 (43, M + ); HRMS calcd for C 18 H 30 O: 262.229 66, found 262.229 51. The 1 H NMR spectrum is in compliance with that described …”

“…According to this procedure, 26 was subjected to reaction with 2 equiv of lithium dimethyl methylphosphonate (THF, −78 °C), whereupon dianion 27 was quenched with 1 equiv of acetic acid. The intermediate monoanions underwent intramolecular cyclization (at 55 °C) to give the target compound 4 as the sole product.…”

Lithium Aluminum Hydride: A Powerful Reducing Agent

“…11 (H) Formation of cyclopropane derivatives A homoallylic mesylate, when subjected to LAH, provided the cyclopropane derivative through homoallylic p-participation. 12…”